linux-vybrid_public/arch/mips/kvm/kvm_mips_emul.c

/*
* This file is subject to the terms and conditions of the GNU General Public
* License.  See the file "COPYING" in the main directory of this archive
* for more details.
*
* KVM/MIPS: Instruction/Exception emulation
*
* Copyright (C) 2012  MIPS Technologies, Inc.  All rights reserved.
* Authors: Sanjay Lal <sanjayl@kymasys.com>
*/

#include <linux/errno.h>
#include <linux/err.h>
#include <linux/kvm_host.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/fs.h>
#include <linux/bootmem.h>
#include <linux/random.h>
#include <asm/page.h>
#include <asm/cacheflush.h>
#include <asm/cpu-info.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
#include <asm/inst.h>

#undef CONFIG_MIPS_MT
#include <asm/r4kcache.h>
#define CONFIG_MIPS_MT

#include "kvm_mips_opcode.h"
#include "kvm_mips_int.h"
#include "kvm_mips_comm.h"

#include "trace.h"

/*
 * Compute the return address and do emulate branch simulation, if required.
 * This function should be called only in branch delay slot active.
 */
unsigned long kvm_compute_return_epc(struct kvm_vcpu *vcpu,
	unsigned long instpc)
{
	unsigned int dspcontrol;
	union mips_instruction insn;
	struct kvm_vcpu_arch *arch = &vcpu->arch;
	long epc = instpc;
	long nextpc = KVM_INVALID_INST;

	if (epc & 3)
		goto unaligned;

	/*
	 * Read the instruction
	 */
	insn.word = kvm_get_inst((uint32_t *) epc, vcpu);

	if (insn.word == KVM_INVALID_INST)
		return KVM_INVALID_INST;

	switch (insn.i_format.opcode) {
		/*
		 * jr and jalr are in r_format format.
		 */
	case spec_op:
		switch (insn.r_format.func) {
		case jalr_op:
			arch->gprs[insn.r_format.rd] = epc + 8;
			/* Fall through */
		case jr_op:
			nextpc = arch->gprs[insn.r_format.rs];
			break;
		}
		break;

		/*
		 * This group contains:
		 * bltz_op, bgez_op, bltzl_op, bgezl_op,
		 * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
		 */
	case bcond_op:
		switch (insn.i_format.rt) {
		case bltz_op:
		case bltzl_op:
			if ((long)arch->gprs[insn.i_format.rs] < 0)
				epc = epc + 4 + (insn.i_format.simmediate << 2);
			else
				epc += 8;
			nextpc = epc;
			break;

		case bgez_op:
		case bgezl_op:
			if ((long)arch->gprs[insn.i_format.rs] >= 0)
				epc = epc + 4 + (insn.i_format.simmediate << 2);
			else
				epc += 8;
			nextpc = epc;
			break;

		case bltzal_op:
		case bltzall_op:
			arch->gprs[31] = epc + 8;
			if ((long)arch->gprs[insn.i_format.rs] < 0)
				epc = epc + 4 + (insn.i_format.simmediate << 2);
			else
				epc += 8;
			nextpc = epc;
			break;

		case bgezal_op:
		case bgezall_op:
			arch->gprs[31] = epc + 8;
			if ((long)arch->gprs[insn.i_format.rs] >= 0)
				epc = epc + 4 + (insn.i_format.simmediate << 2);
			else
				epc += 8;
			nextpc = epc;
			break;
		case bposge32_op:
			if (!cpu_has_dsp)
				goto sigill;

			dspcontrol = rddsp(0x01);

			if (dspcontrol >= 32) {
				epc = epc + 4 + (insn.i_format.simmediate << 2);
			} else
				epc += 8;
			nextpc = epc;
			break;
		}
		break;

		/*
		 * These are unconditional and in j_format.
		 */
	case jal_op:
		arch->gprs[31] = instpc + 8;
	case j_op:
		epc += 4;
		epc >>= 28;
		epc <<= 28;
		epc |= (insn.j_format.target << 2);
		nextpc = epc;
		break;

		/*
		 * These are conditional and in i_format.
		 */
	case beq_op:
	case beql_op:
		if (arch->gprs[insn.i_format.rs] ==
		    arch->gprs[insn.i_format.rt])
			epc = epc + 4 + (insn.i_format.simmediate << 2);
		else
			epc += 8;
		nextpc = epc;
		break;

	case bne_op:
	case bnel_op:
		if (arch->gprs[insn.i_format.rs] !=
		    arch->gprs[insn.i_format.rt])
			epc = epc + 4 + (insn.i_format.simmediate << 2);
		else
			epc += 8;
		nextpc = epc;
		break;

	case blez_op:		/* not really i_format */
	case blezl_op:
		/* rt field assumed to be zero */
		if ((long)arch->gprs[insn.i_format.rs] <= 0)
			epc = epc + 4 + (insn.i_format.simmediate << 2);
		else
			epc += 8;
		nextpc = epc;
		break;

	case bgtz_op:
	case bgtzl_op:
		/* rt field assumed to be zero */
		if ((long)arch->gprs[insn.i_format.rs] > 0)
			epc = epc + 4 + (insn.i_format.simmediate << 2);
		else
			epc += 8;
		nextpc = epc;
		break;

		/*
		 * And now the FPA/cp1 branch instructions.
		 */
	case cop1_op:
		printk("%s: unsupported cop1_op\n", __func__);
		break;
	}

	return nextpc;

unaligned:
	printk("%s: unaligned epc\n", __func__);
	return nextpc;

sigill:
	printk("%s: DSP branch but not DSP ASE\n", __func__);
	return nextpc;
}

enum emulation_result update_pc(struct kvm_vcpu *vcpu, uint32_t cause)
{
	unsigned long branch_pc;
	enum emulation_result er = EMULATE_DONE;

	if (cause & CAUSEF_BD) {
		branch_pc = kvm_compute_return_epc(vcpu, vcpu->arch.pc);
		if (branch_pc == KVM_INVALID_INST) {
			er = EMULATE_FAIL;
		} else {
			vcpu->arch.pc = branch_pc;
			kvm_debug("BD update_pc(): New PC: %#lx\n", vcpu->arch.pc);
		}
	} else
		vcpu->arch.pc += 4;

	kvm_debug("update_pc(): New PC: %#lx\n", vcpu->arch.pc);

	return er;
}

/* Everytime the compare register is written to, we need to decide when to fire
 * the timer that represents timer ticks to the GUEST.
 *
 */
enum emulation_result kvm_mips_emulate_count(struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	enum emulation_result er = EMULATE_DONE;

	/* If COUNT is enabled */
	if (!(kvm_read_c0_guest_cause(cop0) & CAUSEF_DC)) {
		hrtimer_try_to_cancel(&vcpu->arch.comparecount_timer);
		hrtimer_start(&vcpu->arch.comparecount_timer,
			      ktime_set(0, MS_TO_NS(10)), HRTIMER_MODE_REL);
	} else {
		hrtimer_try_to_cancel(&vcpu->arch.comparecount_timer);
	}

	return er;
}

enum emulation_result kvm_mips_emul_eret(struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	enum emulation_result er = EMULATE_DONE;

	if (kvm_read_c0_guest_status(cop0) & ST0_EXL) {
		kvm_debug("[%#lx] ERET to %#lx\n", vcpu->arch.pc,
			  kvm_read_c0_guest_epc(cop0));
		kvm_clear_c0_guest_status(cop0, ST0_EXL);
		vcpu->arch.pc = kvm_read_c0_guest_epc(cop0);

	} else if (kvm_read_c0_guest_status(cop0) & ST0_ERL) {
		kvm_clear_c0_guest_status(cop0, ST0_ERL);
		vcpu->arch.pc = kvm_read_c0_guest_errorepc(cop0);
	} else {
		printk("[%#lx] ERET when MIPS_SR_EXL|MIPS_SR_ERL == 0\n",
		       vcpu->arch.pc);
		er = EMULATE_FAIL;
	}

	return er;
}

enum emulation_result kvm_mips_emul_wait(struct kvm_vcpu *vcpu)
{
	enum emulation_result er = EMULATE_DONE;

	kvm_debug("[%#lx] !!!WAIT!!! (%#lx)\n", vcpu->arch.pc,
		  vcpu->arch.pending_exceptions);

	++vcpu->stat.wait_exits;
	trace_kvm_exit(vcpu, WAIT_EXITS);
	if (!vcpu->arch.pending_exceptions) {
		vcpu->arch.wait = 1;
		kvm_vcpu_block(vcpu);

		/* We we are runnable, then definitely go off to user space to check if any
		 * I/O interrupts are pending.
		 */
		if (kvm_check_request(KVM_REQ_UNHALT, vcpu)) {
			clear_bit(KVM_REQ_UNHALT, &vcpu->requests);
			vcpu->run->exit_reason = KVM_EXIT_IRQ_WINDOW_OPEN;
		}
	}

	return er;
}

/* XXXKYMA: Linux doesn't seem to use TLBR, return EMULATE_FAIL for now so that we can catch
 * this, if things ever change
 */
enum emulation_result kvm_mips_emul_tlbr(struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	enum emulation_result er = EMULATE_FAIL;
	uint32_t pc = vcpu->arch.pc;

	printk("[%#x] COP0_TLBR [%ld]\n", pc, kvm_read_c0_guest_index(cop0));
	return er;
}

/* Write Guest TLB Entry @ Index */
enum emulation_result kvm_mips_emul_tlbwi(struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	int index = kvm_read_c0_guest_index(cop0);
	enum emulation_result er = EMULATE_DONE;
	struct kvm_mips_tlb *tlb = NULL;
	uint32_t pc = vcpu->arch.pc;

	if (index < 0 || index >= KVM_MIPS_GUEST_TLB_SIZE) {
		printk("%s: illegal index: %d\n", __func__, index);
		printk
		    ("[%#x] COP0_TLBWI [%d] (entryhi: %#lx, entrylo0: %#lx entrylo1: %#lx, mask: %#lx)\n",
		     pc, index, kvm_read_c0_guest_entryhi(cop0),
		     kvm_read_c0_guest_entrylo0(cop0),
		     kvm_read_c0_guest_entrylo1(cop0),
		     kvm_read_c0_guest_pagemask(cop0));
		index = (index & ~0x80000000) % KVM_MIPS_GUEST_TLB_SIZE;
	}

	tlb = &vcpu->arch.guest_tlb[index];
#if 1
	/* Probe the shadow host TLB for the entry being overwritten, if one matches, invalidate it */
	kvm_mips_host_tlb_inv(vcpu, tlb->tlb_hi);
#endif

	tlb->tlb_mask = kvm_read_c0_guest_pagemask(cop0);
	tlb->tlb_hi = kvm_read_c0_guest_entryhi(cop0);
	tlb->tlb_lo0 = kvm_read_c0_guest_entrylo0(cop0);
	tlb->tlb_lo1 = kvm_read_c0_guest_entrylo1(cop0);

	kvm_debug
	    ("[%#x] COP0_TLBWI [%d] (entryhi: %#lx, entrylo0: %#lx entrylo1: %#lx, mask: %#lx)\n",
	     pc, index, kvm_read_c0_guest_entryhi(cop0),
	     kvm_read_c0_guest_entrylo0(cop0), kvm_read_c0_guest_entrylo1(cop0),
	     kvm_read_c0_guest_pagemask(cop0));

	return er;
}

/* Write Guest TLB Entry @ Random Index */
enum emulation_result kvm_mips_emul_tlbwr(struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	enum emulation_result er = EMULATE_DONE;
	struct kvm_mips_tlb *tlb = NULL;
	uint32_t pc = vcpu->arch.pc;
	int index;

#if 1
	get_random_bytes(&index, sizeof(index));
	index &= (KVM_MIPS_GUEST_TLB_SIZE - 1);
#else
	index = jiffies % KVM_MIPS_GUEST_TLB_SIZE;
#endif

	if (index < 0 || index >= KVM_MIPS_GUEST_TLB_SIZE) {
		printk("%s: illegal index: %d\n", __func__, index);
		return EMULATE_FAIL;
	}

	tlb = &vcpu->arch.guest_tlb[index];

#if 1
	/* Probe the shadow host TLB for the entry being overwritten, if one matches, invalidate it */
	kvm_mips_host_tlb_inv(vcpu, tlb->tlb_hi);
#endif

	tlb->tlb_mask = kvm_read_c0_guest_pagemask(cop0);
	tlb->tlb_hi = kvm_read_c0_guest_entryhi(cop0);
	tlb->tlb_lo0 = kvm_read_c0_guest_entrylo0(cop0);
	tlb->tlb_lo1 = kvm_read_c0_guest_entrylo1(cop0);

	kvm_debug
	    ("[%#x] COP0_TLBWR[%d] (entryhi: %#lx, entrylo0: %#lx entrylo1: %#lx)\n",
	     pc, index, kvm_read_c0_guest_entryhi(cop0),
	     kvm_read_c0_guest_entrylo0(cop0),
	     kvm_read_c0_guest_entrylo1(cop0));

	return er;
}

enum emulation_result kvm_mips_emul_tlbp(struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	long entryhi = kvm_read_c0_guest_entryhi(cop0);
	enum emulation_result er = EMULATE_DONE;
	uint32_t pc = vcpu->arch.pc;
	int index = -1;

	index = kvm_mips_guest_tlb_lookup(vcpu, entryhi);

	kvm_write_c0_guest_index(cop0, index);

	kvm_debug("[%#x] COP0_TLBP (entryhi: %#lx), index: %d\n", pc, entryhi,
		  index);

	return er;
}

enum emulation_result
kvm_mips_emulate_CP0(uint32_t inst, uint32_t *opc, uint32_t cause,
		     struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	enum emulation_result er = EMULATE_DONE;
	int32_t rt, rd, copz, sel, co_bit, op;
	uint32_t pc = vcpu->arch.pc;
	unsigned long curr_pc;

	/*
	 * Update PC and hold onto current PC in case there is
	 * an error and we want to rollback the PC
	 */
	curr_pc = vcpu->arch.pc;
	er = update_pc(vcpu, cause);
	if (er == EMULATE_FAIL) {
		return er;
	}

	copz = (inst >> 21) & 0x1f;
	rt = (inst >> 16) & 0x1f;
	rd = (inst >> 11) & 0x1f;
	sel = inst & 0x7;
	co_bit = (inst >> 25) & 1;

	/* Verify that the register is valid */
	if (rd > MIPS_CP0_DESAVE) {
		printk("Invalid rd: %d\n", rd);
		er = EMULATE_FAIL;
		goto done;
	}

	if (co_bit) {
		op = (inst) & 0xff;

		switch (op) {
		case tlbr_op:	/*  Read indexed TLB entry  */
			er = kvm_mips_emul_tlbr(vcpu);
			break;
		case tlbwi_op:	/*  Write indexed  */
			er = kvm_mips_emul_tlbwi(vcpu);
			break;
		case tlbwr_op:	/*  Write random  */
			er = kvm_mips_emul_tlbwr(vcpu);
			break;
		case tlbp_op:	/* TLB Probe */
			er = kvm_mips_emul_tlbp(vcpu);
			break;
		case rfe_op:
			printk("!!!COP0_RFE!!!\n");
			break;
		case eret_op:
			er = kvm_mips_emul_eret(vcpu);
			goto dont_update_pc;
			break;
		case wait_op:
			er = kvm_mips_emul_wait(vcpu);
			break;
		}
	} else {
		switch (copz) {
		case mfc_op:
#ifdef CONFIG_KVM_MIPS_DEBUG_COP0_COUNTERS
			cop0->stat[rd][sel]++;
#endif
			/* Get reg */
			if ((rd == MIPS_CP0_COUNT) && (sel == 0)) {
				/* XXXKYMA: Run the Guest count register @ 1/4 the rate of the host */
				vcpu->arch.gprs[rt] = (read_c0_count() >> 2);
			} else if ((rd == MIPS_CP0_ERRCTL) && (sel == 0)) {
				vcpu->arch.gprs[rt] = 0x0;
#ifdef CONFIG_KVM_MIPS_DYN_TRANS
				kvm_mips_trans_mfc0(inst, opc, vcpu);
#endif
			}
			else {
				vcpu->arch.gprs[rt] = cop0->reg[rd][sel];

#ifdef CONFIG_KVM_MIPS_DYN_TRANS
				kvm_mips_trans_mfc0(inst, opc, vcpu);
#endif
			}

			kvm_debug
			    ("[%#x] MFCz[%d][%d], vcpu->arch.gprs[%d]: %#lx\n",
			     pc, rd, sel, rt, vcpu->arch.gprs[rt]);

			break;

		case dmfc_op:
			vcpu->arch.gprs[rt] = cop0->reg[rd][sel];
			break;

		case mtc_op:
#ifdef CONFIG_KVM_MIPS_DEBUG_COP0_COUNTERS
			cop0->stat[rd][sel]++;
#endif
			if ((rd == MIPS_CP0_TLB_INDEX)
			    && (vcpu->arch.gprs[rt] >=
				KVM_MIPS_GUEST_TLB_SIZE)) {
				printk("Invalid TLB Index: %ld",
				       vcpu->arch.gprs[rt]);
				er = EMULATE_FAIL;
				break;
			}
#define C0_EBASE_CORE_MASK 0xff
			if ((rd == MIPS_CP0_PRID) && (sel == 1)) {
				/* Preserve CORE number */
				kvm_change_c0_guest_ebase(cop0,
							  ~(C0_EBASE_CORE_MASK),
							  vcpu->arch.gprs[rt]);
				printk("MTCz, cop0->reg[EBASE]: %#lx\n",
				       kvm_read_c0_guest_ebase(cop0));
			} else if (rd == MIPS_CP0_TLB_HI && sel == 0) {
				uint32_t nasid =
				    vcpu->arch.gprs[rt] & ASID_MASK;
				if ((KSEGX(vcpu->arch.gprs[rt]) != CKSEG0)
				    &&
				    ((kvm_read_c0_guest_entryhi(cop0) &
				      ASID_MASK) != nasid)) {

					kvm_debug
					    ("MTCz, change ASID from %#lx to %#lx\n",
					     kvm_read_c0_guest_entryhi(cop0) &
					     ASID_MASK,
					     vcpu->arch.gprs[rt] & ASID_MASK);

					/* Blow away the shadow host TLBs */
					kvm_mips_flush_host_tlb(1);
				}
				kvm_write_c0_guest_entryhi(cop0,
							   vcpu->arch.gprs[rt]);
			}
			/* Are we writing to COUNT */
			else if ((rd == MIPS_CP0_COUNT) && (sel == 0)) {
				/* Linux doesn't seem to write into COUNT, we throw an error
				 * if we notice a write to COUNT
				 */
				/*er = EMULATE_FAIL; */
				goto done;
			} else if ((rd == MIPS_CP0_COMPARE) && (sel == 0)) {
				kvm_debug("[%#x] MTCz, COMPARE %#lx <- %#lx\n",
					  pc, kvm_read_c0_guest_compare(cop0),
					  vcpu->arch.gprs[rt]);

				/* If we are writing to COMPARE */
				/* Clear pending timer interrupt, if any */
				kvm_mips_callbacks->dequeue_timer_int(vcpu);
				kvm_write_c0_guest_compare(cop0,
							   vcpu->arch.gprs[rt]);
			} else if ((rd == MIPS_CP0_STATUS) && (sel == 0)) {
				kvm_write_c0_guest_status(cop0,
							  vcpu->arch.gprs[rt]);
				/* Make sure that CU1 and NMI bits are never set */
				kvm_clear_c0_guest_status(cop0,
							  (ST0_CU1 | ST0_NMI));

#ifdef CONFIG_KVM_MIPS_DYN_TRANS
				kvm_mips_trans_mtc0(inst, opc, vcpu);
#endif
			} else {
				cop0->reg[rd][sel] = vcpu->arch.gprs[rt];
#ifdef CONFIG_KVM_MIPS_DYN_TRANS
				kvm_mips_trans_mtc0(inst, opc, vcpu);
#endif
			}

			kvm_debug("[%#x] MTCz, cop0->reg[%d][%d]: %#lx\n", pc,
				  rd, sel, cop0->reg[rd][sel]);
			break;

		case dmtc_op:
			printk
			    ("!!!!!!![%#lx]dmtc_op: rt: %d, rd: %d, sel: %d!!!!!!\n",
			     vcpu->arch.pc, rt, rd, sel);
			er = EMULATE_FAIL;
			break;

		case mfmcz_op:
#ifdef KVM_MIPS_DEBUG_COP0_COUNTERS
			cop0->stat[MIPS_CP0_STATUS][0]++;
#endif
			if (rt != 0) {
				vcpu->arch.gprs[rt] =
				    kvm_read_c0_guest_status(cop0);
			}
			/* EI */
			if (inst & 0x20) {
				kvm_debug("[%#lx] mfmcz_op: EI\n",
					  vcpu->arch.pc);
				kvm_set_c0_guest_status(cop0, ST0_IE);
			} else {
				kvm_debug("[%#lx] mfmcz_op: DI\n",
					  vcpu->arch.pc);
				kvm_clear_c0_guest_status(cop0, ST0_IE);
			}

			break;

		case wrpgpr_op:
			{
				uint32_t css =
				    cop0->reg[MIPS_CP0_STATUS][2] & 0xf;
				uint32_t pss =
				    (cop0->reg[MIPS_CP0_STATUS][2] >> 6) & 0xf;
				/* We don't support any shadow register sets, so SRSCtl[PSS] == SRSCtl[CSS] = 0 */
				if (css || pss) {
					er = EMULATE_FAIL;
					break;
				}
				kvm_debug("WRPGPR[%d][%d] = %#lx\n", pss, rd,
					  vcpu->arch.gprs[rt]);
				vcpu->arch.gprs[rd] = vcpu->arch.gprs[rt];
			}
			break;
		default:
			printk
			    ("[%#lx]MachEmulateCP0: unsupported COP0, copz: 0x%x\n",
			     vcpu->arch.pc, copz);
			er = EMULATE_FAIL;
			break;
		}
	}

done:
	/*
	 * Rollback PC only if emulation was unsuccessful
	 */
	if (er == EMULATE_FAIL) {
		vcpu->arch.pc = curr_pc;
	}

dont_update_pc:
	/*
	 * This is for special instructions whose emulation
	 * updates the PC, so do not overwrite the PC under
	 * any circumstances
	 */

	return er;
}

enum emulation_result
kvm_mips_emulate_store(uint32_t inst, uint32_t cause,
		       struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	enum emulation_result er = EMULATE_DO_MMIO;
	int32_t op, base, rt, offset;
	uint32_t bytes;
	void *data = run->mmio.data;
	unsigned long curr_pc;

	/*
	 * Update PC and hold onto current PC in case there is
	 * an error and we want to rollback the PC
	 */
	curr_pc = vcpu->arch.pc;
	er = update_pc(vcpu, cause);
	if (er == EMULATE_FAIL)
		return er;

	rt = (inst >> 16) & 0x1f;
	base = (inst >> 21) & 0x1f;
	offset = inst & 0xffff;
	op = (inst >> 26) & 0x3f;

	switch (op) {
	case sb_op:
		bytes = 1;
		if (bytes > sizeof(run->mmio.data)) {
			kvm_err("%s: bad MMIO length: %d\n", __func__,
			       run->mmio.len);
		}
		run->mmio.phys_addr =
		    kvm_mips_callbacks->gva_to_gpa(vcpu->arch.
						   host_cp0_badvaddr);
		if (run->mmio.phys_addr == KVM_INVALID_ADDR) {
			er = EMULATE_FAIL;
			break;
		}
		run->mmio.len = bytes;
		run->mmio.is_write = 1;
		vcpu->mmio_needed = 1;
		vcpu->mmio_is_write = 1;
		*(u8 *) data = vcpu->arch.gprs[rt];
		kvm_debug("OP_SB: eaddr: %#lx, gpr: %#lx, data: %#x\n",
			  vcpu->arch.host_cp0_badvaddr, vcpu->arch.gprs[rt],
			  *(uint8_t *) data);

		break;

	case sw_op:
		bytes = 4;
		if (bytes > sizeof(run->mmio.data)) {
			kvm_err("%s: bad MMIO length: %d\n", __func__,
			       run->mmio.len);
		}
		run->mmio.phys_addr =
		    kvm_mips_callbacks->gva_to_gpa(vcpu->arch.
						   host_cp0_badvaddr);
		if (run->mmio.phys_addr == KVM_INVALID_ADDR) {
			er = EMULATE_FAIL;
			break;
		}

		run->mmio.len = bytes;
		run->mmio.is_write = 1;
		vcpu->mmio_needed = 1;
		vcpu->mmio_is_write = 1;
		*(uint32_t *) data = vcpu->arch.gprs[rt];

		kvm_debug("[%#lx] OP_SW: eaddr: %#lx, gpr: %#lx, data: %#x\n",
			  vcpu->arch.pc, vcpu->arch.host_cp0_badvaddr,
			  vcpu->arch.gprs[rt], *(uint32_t *) data);
		break;

	case sh_op:
		bytes = 2;
		if (bytes > sizeof(run->mmio.data)) {
			kvm_err("%s: bad MMIO length: %d\n", __func__,
			       run->mmio.len);
		}
		run->mmio.phys_addr =
		    kvm_mips_callbacks->gva_to_gpa(vcpu->arch.
						   host_cp0_badvaddr);
		if (run->mmio.phys_addr == KVM_INVALID_ADDR) {
			er = EMULATE_FAIL;
			break;
		}

		run->mmio.len = bytes;
		run->mmio.is_write = 1;
		vcpu->mmio_needed = 1;
		vcpu->mmio_is_write = 1;
		*(uint16_t *) data = vcpu->arch.gprs[rt];

		kvm_debug("[%#lx] OP_SH: eaddr: %#lx, gpr: %#lx, data: %#x\n",
			  vcpu->arch.pc, vcpu->arch.host_cp0_badvaddr,
			  vcpu->arch.gprs[rt], *(uint32_t *) data);
		break;

	default:
		printk("Store not yet supported");
		er = EMULATE_FAIL;
		break;
	}

	/*
	 * Rollback PC if emulation was unsuccessful
	 */
	if (er == EMULATE_FAIL) {
		vcpu->arch.pc = curr_pc;
	}

	return er;
}

enum emulation_result
kvm_mips_emulate_load(uint32_t inst, uint32_t cause,
		      struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	enum emulation_result er = EMULATE_DO_MMIO;
	int32_t op, base, rt, offset;
	uint32_t bytes;

	rt = (inst >> 16) & 0x1f;
	base = (inst >> 21) & 0x1f;
	offset = inst & 0xffff;
	op = (inst >> 26) & 0x3f;

	vcpu->arch.pending_load_cause = cause;
	vcpu->arch.io_gpr = rt;

	switch (op) {
	case lw_op:
		bytes = 4;
		if (bytes > sizeof(run->mmio.data)) {
			kvm_err("%s: bad MMIO length: %d\n", __func__,
			       run->mmio.len);
			er = EMULATE_FAIL;
			break;
		}
		run->mmio.phys_addr =
		    kvm_mips_callbacks->gva_to_gpa(vcpu->arch.
						   host_cp0_badvaddr);
		if (run->mmio.phys_addr == KVM_INVALID_ADDR) {
			er = EMULATE_FAIL;
			break;
		}

		run->mmio.len = bytes;
		run->mmio.is_write = 0;
		vcpu->mmio_needed = 1;
		vcpu->mmio_is_write = 0;
		break;

	case lh_op:
	case lhu_op:
		bytes = 2;
		if (bytes > sizeof(run->mmio.data)) {
			kvm_err("%s: bad MMIO length: %d\n", __func__,
			       run->mmio.len);
			er = EMULATE_FAIL;
			break;
		}
		run->mmio.phys_addr =
		    kvm_mips_callbacks->gva_to_gpa(vcpu->arch.
						   host_cp0_badvaddr);
		if (run->mmio.phys_addr == KVM_INVALID_ADDR) {
			er = EMULATE_FAIL;
			break;
		}

		run->mmio.len = bytes;
		run->mmio.is_write = 0;
		vcpu->mmio_needed = 1;
		vcpu->mmio_is_write = 0;

		if (op == lh_op)
			vcpu->mmio_needed = 2;
		else
			vcpu->mmio_needed = 1;

		break;

	case lbu_op:
	case lb_op:
		bytes = 1;
		if (bytes > sizeof(run->mmio.data)) {
			kvm_err("%s: bad MMIO length: %d\n", __func__,
			       run->mmio.len);
			er = EMULATE_FAIL;
			break;
		}
		run->mmio.phys_addr =
		    kvm_mips_callbacks->gva_to_gpa(vcpu->arch.
						   host_cp0_badvaddr);
		if (run->mmio.phys_addr == KVM_INVALID_ADDR) {
			er = EMULATE_FAIL;
			break;
		}

		run->mmio.len = bytes;
		run->mmio.is_write = 0;
		vcpu->mmio_is_write = 0;

		if (op == lb_op)
			vcpu->mmio_needed = 2;
		else
			vcpu->mmio_needed = 1;

		break;

	default:
		printk("Load not yet supported");
		er = EMULATE_FAIL;
		break;
	}

	return er;
}

int kvm_mips_sync_icache(unsigned long va, struct kvm_vcpu *vcpu)
{
	unsigned long offset = (va & ~PAGE_MASK);
	struct kvm *kvm = vcpu->kvm;
	unsigned long pa;
	gfn_t gfn;
	pfn_t pfn;

	gfn = va >> PAGE_SHIFT;

	if (gfn >= kvm->arch.guest_pmap_npages) {
		printk("%s: Invalid gfn: %#llx\n", __func__, gfn);
		kvm_mips_dump_host_tlbs();
		kvm_arch_vcpu_dump_regs(vcpu);
		return -1;
	}
	pfn = kvm->arch.guest_pmap[gfn];
	pa = (pfn << PAGE_SHIFT) | offset;

	printk("%s: va: %#lx, unmapped: %#x\n", __func__, va, CKSEG0ADDR(pa));

	mips32_SyncICache(CKSEG0ADDR(pa), 32);
	return 0;
}

#define MIPS_CACHE_OP_INDEX_INV         0x0
#define MIPS_CACHE_OP_INDEX_LD_TAG      0x1
#define MIPS_CACHE_OP_INDEX_ST_TAG      0x2
#define MIPS_CACHE_OP_IMP               0x3
#define MIPS_CACHE_OP_HIT_INV           0x4
#define MIPS_CACHE_OP_FILL_WB_INV       0x5
#define MIPS_CACHE_OP_HIT_HB            0x6
#define MIPS_CACHE_OP_FETCH_LOCK        0x7

#define MIPS_CACHE_ICACHE               0x0
#define MIPS_CACHE_DCACHE               0x1
#define MIPS_CACHE_SEC                  0x3

enum emulation_result
kvm_mips_emulate_cache(uint32_t inst, uint32_t *opc, uint32_t cause,
		       struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	extern void (*r4k_blast_dcache) (void);
	extern void (*r4k_blast_icache) (void);
	enum emulation_result er = EMULATE_DONE;
	int32_t offset, cache, op_inst, op, base;
	struct kvm_vcpu_arch *arch = &vcpu->arch;
	unsigned long va;
	unsigned long curr_pc;

	/*
	 * Update PC and hold onto current PC in case there is
	 * an error and we want to rollback the PC
	 */
	curr_pc = vcpu->arch.pc;
	er = update_pc(vcpu, cause);
	if (er == EMULATE_FAIL)
		return er;

	base = (inst >> 21) & 0x1f;
	op_inst = (inst >> 16) & 0x1f;
	offset = inst & 0xffff;
	cache = (inst >> 16) & 0x3;
	op = (inst >> 18) & 0x7;

	va = arch->gprs[base] + offset;

	kvm_debug("CACHE (cache: %#x, op: %#x, base[%d]: %#lx, offset: %#x\n",
		  cache, op, base, arch->gprs[base], offset);

	/* Treat INDEX_INV as a nop, basically issued by Linux on startup to invalidate
	 * the caches entirely by stepping through all the ways/indexes
	 */
	if (op == MIPS_CACHE_OP_INDEX_INV) {
		kvm_debug
		    ("@ %#lx/%#lx CACHE (cache: %#x, op: %#x, base[%d]: %#lx, offset: %#x\n",
		     vcpu->arch.pc, vcpu->arch.gprs[31], cache, op, base,
		     arch->gprs[base], offset);

		if (cache == MIPS_CACHE_DCACHE)
			r4k_blast_dcache();
		else if (cache == MIPS_CACHE_ICACHE)
			r4k_blast_icache();
		else {
			printk("%s: unsupported CACHE INDEX operation\n",
			       __func__);
			return EMULATE_FAIL;
		}

#ifdef CONFIG_KVM_MIPS_DYN_TRANS
		kvm_mips_trans_cache_index(inst, opc, vcpu);
#endif
		goto done;
	}

	preempt_disable();
	if (KVM_GUEST_KSEGX(va) == KVM_GUEST_KSEG0) {

		if (kvm_mips_host_tlb_lookup(vcpu, va) < 0) {
			kvm_mips_handle_kseg0_tlb_fault(va, vcpu);
		}
	} else if ((KVM_GUEST_KSEGX(va) < KVM_GUEST_KSEG0) ||
		   KVM_GUEST_KSEGX(va) == KVM_GUEST_KSEG23) {
		int index;

		/* If an entry already exists then skip */
		if (kvm_mips_host_tlb_lookup(vcpu, va) >= 0) {
			goto skip_fault;
		}

		/* If address not in the guest TLB, then give the guest a fault, the
		 * resulting handler will do the right thing
		 */
		index = kvm_mips_guest_tlb_lookup(vcpu, (va & VPN2_MASK) |
						  (kvm_read_c0_guest_entryhi
						   (cop0) & ASID_MASK));

		if (index < 0) {
			vcpu->arch.host_cp0_entryhi = (va & VPN2_MASK);
			vcpu->arch.host_cp0_badvaddr = va;
			er = kvm_mips_emulate_tlbmiss_ld(cause, NULL, run,
							 vcpu);
			preempt_enable();
			goto dont_update_pc;
		} else {
			struct kvm_mips_tlb *tlb = &vcpu->arch.guest_tlb[index];
			/* Check if the entry is valid, if not then setup a TLB invalid exception to the guest */
			if (!TLB_IS_VALID(*tlb, va)) {
				er = kvm_mips_emulate_tlbinv_ld(cause, NULL,
								run, vcpu);
				preempt_enable();
				goto dont_update_pc;
			} else {
				/* We fault an entry from the guest tlb to the shadow host TLB */
				kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb,
								     NULL,
								     NULL);
			}
		}
	} else {
		printk
		    ("INVALID CACHE INDEX/ADDRESS (cache: %#x, op: %#x, base[%d]: %#lx, offset: %#x\n",
		     cache, op, base, arch->gprs[base], offset);
		er = EMULATE_FAIL;
		preempt_enable();
		goto dont_update_pc;

	}

skip_fault:
	/* XXXKYMA: Only a subset of cache ops are supported, used by Linux */
	if (cache == MIPS_CACHE_DCACHE
	    && (op == MIPS_CACHE_OP_FILL_WB_INV
		|| op == MIPS_CACHE_OP_HIT_INV)) {
		flush_dcache_line(va);

#ifdef CONFIG_KVM_MIPS_DYN_TRANS
		/* Replace the CACHE instruction, with a SYNCI, not the same, but avoids a trap */
		kvm_mips_trans_cache_va(inst, opc, vcpu);
#endif
	} else if (op == MIPS_CACHE_OP_HIT_INV && cache == MIPS_CACHE_ICACHE) {
		flush_dcache_line(va);
		flush_icache_line(va);

#ifdef CONFIG_KVM_MIPS_DYN_TRANS
		/* Replace the CACHE instruction, with a SYNCI */
		kvm_mips_trans_cache_va(inst, opc, vcpu);
#endif
	} else {
		printk
		    ("NO-OP CACHE (cache: %#x, op: %#x, base[%d]: %#lx, offset: %#x\n",
		     cache, op, base, arch->gprs[base], offset);
		er = EMULATE_FAIL;
		preempt_enable();
		goto dont_update_pc;
	}

	preempt_enable();

      dont_update_pc:
	/*
	 * Rollback PC
	 */
	vcpu->arch.pc = curr_pc;
      done:
	return er;
}

enum emulation_result
kvm_mips_emulate_inst(unsigned long cause, uint32_t *opc,
		      struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	enum emulation_result er = EMULATE_DONE;
	uint32_t inst;

	/*
	 *  Fetch the instruction.
	 */
	if (cause & CAUSEF_BD) {
		opc += 1;
	}

	inst = kvm_get_inst(opc, vcpu);

	switch (((union mips_instruction)inst).r_format.opcode) {
	case cop0_op:
		er = kvm_mips_emulate_CP0(inst, opc, cause, run, vcpu);
		break;
	case sb_op:
	case sh_op:
	case sw_op:
		er = kvm_mips_emulate_store(inst, cause, run, vcpu);
		break;
	case lb_op:
	case lbu_op:
	case lhu_op:
	case lh_op:
	case lw_op:
		er = kvm_mips_emulate_load(inst, cause, run, vcpu);
		break;

	case cache_op:
		++vcpu->stat.cache_exits;
		trace_kvm_exit(vcpu, CACHE_EXITS);
		er = kvm_mips_emulate_cache(inst, opc, cause, run, vcpu);
		break;

	default:
		printk("Instruction emulation not supported (%p/%#x)\n", opc,
		       inst);
		kvm_arch_vcpu_dump_regs(vcpu);
		er = EMULATE_FAIL;
		break;
	}

	return er;
}

enum emulation_result
kvm_mips_emulate_syscall(unsigned long cause, uint32_t *opc,
			 struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	struct kvm_vcpu_arch *arch = &vcpu->arch;
	enum emulation_result er = EMULATE_DONE;

	if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
		/* save old pc */
		kvm_write_c0_guest_epc(cop0, arch->pc);
		kvm_set_c0_guest_status(cop0, ST0_EXL);

		if (cause & CAUSEF_BD)
			kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
		else
			kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

		kvm_debug("Delivering SYSCALL @ pc %#lx\n", arch->pc);

		kvm_change_c0_guest_cause(cop0, (0xff),
					  (T_SYSCALL << CAUSEB_EXCCODE));

		/* Set PC to the exception entry point */
		arch->pc = KVM_GUEST_KSEG0 + 0x180;

	} else {
		printk("Trying to deliver SYSCALL when EXL is already set\n");
		er = EMULATE_FAIL;
	}

	return er;
}

enum emulation_result
kvm_mips_emulate_tlbmiss_ld(unsigned long cause, uint32_t *opc,
			    struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	struct kvm_vcpu_arch *arch = &vcpu->arch;
	enum emulation_result er = EMULATE_DONE;
	unsigned long entryhi = (vcpu->arch.  host_cp0_badvaddr & VPN2_MASK) |
				(kvm_read_c0_guest_entryhi(cop0) & ASID_MASK);

	if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
		/* save old pc */
		kvm_write_c0_guest_epc(cop0, arch->pc);
		kvm_set_c0_guest_status(cop0, ST0_EXL);

		if (cause & CAUSEF_BD)
			kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
		else
			kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

		kvm_debug("[EXL == 0] delivering TLB MISS @ pc %#lx\n",
			  arch->pc);

		/* set pc to the exception entry point */
		arch->pc = KVM_GUEST_KSEG0 + 0x0;

	} else {
		kvm_debug("[EXL == 1] delivering TLB MISS @ pc %#lx\n",
			  arch->pc);

		arch->pc = KVM_GUEST_KSEG0 + 0x180;
	}

	kvm_change_c0_guest_cause(cop0, (0xff),
				  (T_TLB_LD_MISS << CAUSEB_EXCCODE));

	/* setup badvaddr, context and entryhi registers for the guest */
	kvm_write_c0_guest_badvaddr(cop0, vcpu->arch.host_cp0_badvaddr);
	/* XXXKYMA: is the context register used by linux??? */
	kvm_write_c0_guest_entryhi(cop0, entryhi);
	/* Blow away the shadow host TLBs */
	kvm_mips_flush_host_tlb(1);

	return er;
}

enum emulation_result
kvm_mips_emulate_tlbinv_ld(unsigned long cause, uint32_t *opc,
			   struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	struct kvm_vcpu_arch *arch = &vcpu->arch;
	enum emulation_result er = EMULATE_DONE;
	unsigned long entryhi =
		(vcpu->arch.host_cp0_badvaddr & VPN2_MASK) |
		(kvm_read_c0_guest_entryhi(cop0) & ASID_MASK);

	if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
		/* save old pc */
		kvm_write_c0_guest_epc(cop0, arch->pc);
		kvm_set_c0_guest_status(cop0, ST0_EXL);

		if (cause & CAUSEF_BD)
			kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
		else
			kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

		kvm_debug("[EXL == 0] delivering TLB INV @ pc %#lx\n",
			  arch->pc);

		/* set pc to the exception entry point */
		arch->pc = KVM_GUEST_KSEG0 + 0x180;

	} else {
		kvm_debug("[EXL == 1] delivering TLB MISS @ pc %#lx\n",
			  arch->pc);
		arch->pc = KVM_GUEST_KSEG0 + 0x180;
	}

	kvm_change_c0_guest_cause(cop0, (0xff),
				  (T_TLB_LD_MISS << CAUSEB_EXCCODE));

	/* setup badvaddr, context and entryhi registers for the guest */
	kvm_write_c0_guest_badvaddr(cop0, vcpu->arch.host_cp0_badvaddr);
	/* XXXKYMA: is the context register used by linux??? */
	kvm_write_c0_guest_entryhi(cop0, entryhi);
	/* Blow away the shadow host TLBs */
	kvm_mips_flush_host_tlb(1);

	return er;
}

enum emulation_result
kvm_mips_emulate_tlbmiss_st(unsigned long cause, uint32_t *opc,
			    struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	struct kvm_vcpu_arch *arch = &vcpu->arch;
	enum emulation_result er = EMULATE_DONE;
	unsigned long entryhi = (vcpu->arch.host_cp0_badvaddr & VPN2_MASK) |
				(kvm_read_c0_guest_entryhi(cop0) & ASID_MASK);

	if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
		/* save old pc */
		kvm_write_c0_guest_epc(cop0, arch->pc);
		kvm_set_c0_guest_status(cop0, ST0_EXL);

		if (cause & CAUSEF_BD)
			kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
		else
			kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

		kvm_debug("[EXL == 0] Delivering TLB MISS @ pc %#lx\n",
			  arch->pc);

		/* Set PC to the exception entry point */
		arch->pc = KVM_GUEST_KSEG0 + 0x0;
	} else {
		kvm_debug("[EXL == 1] Delivering TLB MISS @ pc %#lx\n",
			  arch->pc);
		arch->pc = KVM_GUEST_KSEG0 + 0x180;
	}

	kvm_change_c0_guest_cause(cop0, (0xff),
				  (T_TLB_ST_MISS << CAUSEB_EXCCODE));

	/* setup badvaddr, context and entryhi registers for the guest */
	kvm_write_c0_guest_badvaddr(cop0, vcpu->arch.host_cp0_badvaddr);
	/* XXXKYMA: is the context register used by linux??? */
	kvm_write_c0_guest_entryhi(cop0, entryhi);
	/* Blow away the shadow host TLBs */
	kvm_mips_flush_host_tlb(1);

	return er;
}

enum emulation_result
kvm_mips_emulate_tlbinv_st(unsigned long cause, uint32_t *opc,
			   struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	struct kvm_vcpu_arch *arch = &vcpu->arch;
	enum emulation_result er = EMULATE_DONE;
	unsigned long entryhi = (vcpu->arch.host_cp0_badvaddr & VPN2_MASK) |
		(kvm_read_c0_guest_entryhi(cop0) & ASID_MASK);

	if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
		/* save old pc */
		kvm_write_c0_guest_epc(cop0, arch->pc);
		kvm_set_c0_guest_status(cop0, ST0_EXL);

		if (cause & CAUSEF_BD)
			kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
		else
			kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

		kvm_debug("[EXL == 0] Delivering TLB MISS @ pc %#lx\n",
			  arch->pc);

		/* Set PC to the exception entry point */
		arch->pc = KVM_GUEST_KSEG0 + 0x180;
	} else {
		kvm_debug("[EXL == 1] Delivering TLB MISS @ pc %#lx\n",
			  arch->pc);
		arch->pc = KVM_GUEST_KSEG0 + 0x180;
	}

	kvm_change_c0_guest_cause(cop0, (0xff),
				  (T_TLB_ST_MISS << CAUSEB_EXCCODE));

	/* setup badvaddr, context and entryhi registers for the guest */
	kvm_write_c0_guest_badvaddr(cop0, vcpu->arch.host_cp0_badvaddr);
	/* XXXKYMA: is the context register used by linux??? */
	kvm_write_c0_guest_entryhi(cop0, entryhi);
	/* Blow away the shadow host TLBs */
	kvm_mips_flush_host_tlb(1);

	return er;
}

/* TLBMOD: store into address matching TLB with Dirty bit off */
enum emulation_result
kvm_mips_handle_tlbmod(unsigned long cause, uint32_t *opc,
		       struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	enum emulation_result er = EMULATE_DONE;

#ifdef DEBUG
	/*
	 * If address not in the guest TLB, then we are in trouble
	 */
	index = kvm_mips_guest_tlb_lookup(vcpu, entryhi);
	if (index < 0) {
		/* XXXKYMA Invalidate and retry */
		kvm_mips_host_tlb_inv(vcpu, vcpu->arch.host_cp0_badvaddr);
		kvm_err("%s: host got TLBMOD for %#lx but entry not present in Guest TLB\n",
		     __func__, entryhi);
		kvm_mips_dump_guest_tlbs(vcpu);
		kvm_mips_dump_host_tlbs();
		return EMULATE_FAIL;
	}
#endif

	er = kvm_mips_emulate_tlbmod(cause, opc, run, vcpu);
	return er;
}

enum emulation_result
kvm_mips_emulate_tlbmod(unsigned long cause, uint32_t *opc,
			struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	unsigned long entryhi = (vcpu->arch.host_cp0_badvaddr & VPN2_MASK) |
				(kvm_read_c0_guest_entryhi(cop0) & ASID_MASK);
	struct kvm_vcpu_arch *arch = &vcpu->arch;
	enum emulation_result er = EMULATE_DONE;

	if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
		/* save old pc */
		kvm_write_c0_guest_epc(cop0, arch->pc);
		kvm_set_c0_guest_status(cop0, ST0_EXL);

		if (cause & CAUSEF_BD)
			kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
		else
			kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

		kvm_debug("[EXL == 0] Delivering TLB MOD @ pc %#lx\n",
			  arch->pc);

		arch->pc = KVM_GUEST_KSEG0 + 0x180;
	} else {
		kvm_debug("[EXL == 1] Delivering TLB MOD @ pc %#lx\n",
			  arch->pc);
		arch->pc = KVM_GUEST_KSEG0 + 0x180;
	}

	kvm_change_c0_guest_cause(cop0, (0xff), (T_TLB_MOD << CAUSEB_EXCCODE));

	/* setup badvaddr, context and entryhi registers for the guest */
	kvm_write_c0_guest_badvaddr(cop0, vcpu->arch.host_cp0_badvaddr);
	/* XXXKYMA: is the context register used by linux??? */
	kvm_write_c0_guest_entryhi(cop0, entryhi);
	/* Blow away the shadow host TLBs */
	kvm_mips_flush_host_tlb(1);

	return er;
}

enum emulation_result
kvm_mips_emulate_fpu_exc(unsigned long cause, uint32_t *opc,
			 struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	struct kvm_vcpu_arch *arch = &vcpu->arch;
	enum emulation_result er = EMULATE_DONE;

	if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
		/* save old pc */
		kvm_write_c0_guest_epc(cop0, arch->pc);
		kvm_set_c0_guest_status(cop0, ST0_EXL);

		if (cause & CAUSEF_BD)
			kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
		else
			kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

	}

	arch->pc = KVM_GUEST_KSEG0 + 0x180;

	kvm_change_c0_guest_cause(cop0, (0xff),
				  (T_COP_UNUSABLE << CAUSEB_EXCCODE));
	kvm_change_c0_guest_cause(cop0, (CAUSEF_CE), (0x1 << CAUSEB_CE));

	return er;
}

enum emulation_result
kvm_mips_emulate_ri_exc(unsigned long cause, uint32_t *opc,
			struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	struct kvm_vcpu_arch *arch = &vcpu->arch;
	enum emulation_result er = EMULATE_DONE;

	if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
		/* save old pc */
		kvm_write_c0_guest_epc(cop0, arch->pc);
		kvm_set_c0_guest_status(cop0, ST0_EXL);

		if (cause & CAUSEF_BD)
			kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
		else
			kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

		kvm_debug("Delivering RI @ pc %#lx\n", arch->pc);

		kvm_change_c0_guest_cause(cop0, (0xff),
					  (T_RES_INST << CAUSEB_EXCCODE));

		/* Set PC to the exception entry point */
		arch->pc = KVM_GUEST_KSEG0 + 0x180;

	} else {
		kvm_err("Trying to deliver RI when EXL is already set\n");
		er = EMULATE_FAIL;
	}

	return er;
}

enum emulation_result
kvm_mips_emulate_bp_exc(unsigned long cause, uint32_t *opc,
			struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	struct kvm_vcpu_arch *arch = &vcpu->arch;
	enum emulation_result er = EMULATE_DONE;

	if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
		/* save old pc */
		kvm_write_c0_guest_epc(cop0, arch->pc);
		kvm_set_c0_guest_status(cop0, ST0_EXL);

		if (cause & CAUSEF_BD)
			kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
		else
			kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

		kvm_debug("Delivering BP @ pc %#lx\n", arch->pc);

		kvm_change_c0_guest_cause(cop0, (0xff),
					  (T_BREAK << CAUSEB_EXCCODE));

		/* Set PC to the exception entry point */
		arch->pc = KVM_GUEST_KSEG0 + 0x180;

	} else {
		printk("Trying to deliver BP when EXL is already set\n");
		er = EMULATE_FAIL;
	}

	return er;
}

/*
 * ll/sc, rdhwr, sync emulation
 */

#define OPCODE 0xfc000000
#define BASE   0x03e00000
#define RT     0x001f0000
#define OFFSET 0x0000ffff
#define LL     0xc0000000
#define SC     0xe0000000
#define SPEC0  0x00000000
#define SPEC3  0x7c000000
#define RD     0x0000f800
#define FUNC   0x0000003f
#define SYNC   0x0000000f
#define RDHWR  0x0000003b

enum emulation_result
kvm_mips_handle_ri(unsigned long cause, uint32_t *opc,
		   struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	struct kvm_vcpu_arch *arch = &vcpu->arch;
	enum emulation_result er = EMULATE_DONE;
	unsigned long curr_pc;
	uint32_t inst;

	/*
	 * Update PC and hold onto current PC in case there is
	 * an error and we want to rollback the PC
	 */
	curr_pc = vcpu->arch.pc;
	er = update_pc(vcpu, cause);
	if (er == EMULATE_FAIL)
		return er;

	/*
	 *  Fetch the instruction.
	 */
	if (cause & CAUSEF_BD)
		opc += 1;

	inst = kvm_get_inst(opc, vcpu);

	if (inst == KVM_INVALID_INST) {
		printk("%s: Cannot get inst @ %p\n", __func__, opc);
		return EMULATE_FAIL;
	}

	if ((inst & OPCODE) == SPEC3 && (inst & FUNC) == RDHWR) {
		int rd = (inst & RD) >> 11;
		int rt = (inst & RT) >> 16;
		switch (rd) {
		case 0:	/* CPU number */
			arch->gprs[rt] = 0;
			break;
		case 1:	/* SYNCI length */
			arch->gprs[rt] = min(current_cpu_data.dcache.linesz,
					     current_cpu_data.icache.linesz);
			break;
		case 2:	/* Read count register */
			printk("RDHWR: Cont register\n");
			arch->gprs[rt] = kvm_read_c0_guest_count(cop0);
			break;
		case 3:	/* Count register resolution */
			switch (current_cpu_data.cputype) {
			case CPU_20KC:
			case CPU_25KF:
				arch->gprs[rt] = 1;
				break;
			default:
				arch->gprs[rt] = 2;
			}
			break;
		case 29:
#if 1
			arch->gprs[rt] = kvm_read_c0_guest_userlocal(cop0);
#else
			/* UserLocal not implemented */
			er = kvm_mips_emulate_ri_exc(cause, opc, run, vcpu);
#endif
			break;

		default:
			printk("RDHWR not supported\n");
			er = EMULATE_FAIL;
			break;
		}
	} else {
		printk("Emulate RI not supported @ %p: %#x\n", opc, inst);
		er = EMULATE_FAIL;
	}

	/*
	 * Rollback PC only if emulation was unsuccessful
	 */
	if (er == EMULATE_FAIL) {
		vcpu->arch.pc = curr_pc;
	}
	return er;
}

enum emulation_result
kvm_mips_complete_mmio_load(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
	unsigned long *gpr = &vcpu->arch.gprs[vcpu->arch.io_gpr];
	enum emulation_result er = EMULATE_DONE;
	unsigned long curr_pc;

	if (run->mmio.len > sizeof(*gpr)) {
		printk("Bad MMIO length: %d", run->mmio.len);
		er = EMULATE_FAIL;
		goto done;
	}

	/*
	 * Update PC and hold onto current PC in case there is
	 * an error and we want to rollback the PC
	 */
	curr_pc = vcpu->arch.pc;
	er = update_pc(vcpu, vcpu->arch.pending_load_cause);
	if (er == EMULATE_FAIL)
		return er;

	switch (run->mmio.len) {
	case 4:
		*gpr = *(int32_t *) run->mmio.data;
		break;

	case 2:
		if (vcpu->mmio_needed == 2)
			*gpr = *(int16_t *) run->mmio.data;
		else
			*gpr = *(int16_t *) run->mmio.data;

		break;
	case 1:
		if (vcpu->mmio_needed == 2)
			*gpr = *(int8_t *) run->mmio.data;
		else
			*gpr = *(u8 *) run->mmio.data;
		break;
	}

	if (vcpu->arch.pending_load_cause & CAUSEF_BD)
		kvm_debug
		    ("[%#lx] Completing %d byte BD Load to gpr %d (0x%08lx) type %d\n",
		     vcpu->arch.pc, run->mmio.len, vcpu->arch.io_gpr, *gpr,
		     vcpu->mmio_needed);

done:
	return er;
}

static enum emulation_result
kvm_mips_emulate_exc(unsigned long cause, uint32_t *opc,
		     struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	uint32_t exccode = (cause >> CAUSEB_EXCCODE) & 0x1f;
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	struct kvm_vcpu_arch *arch = &vcpu->arch;
	enum emulation_result er = EMULATE_DONE;

	if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
		/* save old pc */
		kvm_write_c0_guest_epc(cop0, arch->pc);
		kvm_set_c0_guest_status(cop0, ST0_EXL);

		if (cause & CAUSEF_BD)
			kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
		else
			kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

		kvm_change_c0_guest_cause(cop0, (0xff),
					  (exccode << CAUSEB_EXCCODE));

		/* Set PC to the exception entry point */
		arch->pc = KVM_GUEST_KSEG0 + 0x180;
		kvm_write_c0_guest_badvaddr(cop0, vcpu->arch.host_cp0_badvaddr);

		kvm_debug("Delivering EXC %d @ pc %#lx, badVaddr: %#lx\n",
			  exccode, kvm_read_c0_guest_epc(cop0),
			  kvm_read_c0_guest_badvaddr(cop0));
	} else {
		printk("Trying to deliver EXC when EXL is already set\n");
		er = EMULATE_FAIL;
	}

	return er;
}

enum emulation_result
kvm_mips_check_privilege(unsigned long cause, uint32_t *opc,
			 struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	enum emulation_result er = EMULATE_DONE;
	uint32_t exccode = (cause >> CAUSEB_EXCCODE) & 0x1f;
	unsigned long badvaddr = vcpu->arch.host_cp0_badvaddr;

	int usermode = !KVM_GUEST_KERNEL_MODE(vcpu);

	if (usermode) {
		switch (exccode) {
		case T_INT:
		case T_SYSCALL:
		case T_BREAK:
		case T_RES_INST:
			break;

		case T_COP_UNUSABLE:
			if (((cause & CAUSEF_CE) >> CAUSEB_CE) == 0)
				er = EMULATE_PRIV_FAIL;
			break;

		case T_TLB_MOD:
			break;

		case T_TLB_LD_MISS:
			/* We we are accessing Guest kernel space, then send an address error exception to the guest */
			if (badvaddr >= (unsigned long) KVM_GUEST_KSEG0) {
				printk("%s: LD MISS @ %#lx\n", __func__,
				       badvaddr);
				cause &= ~0xff;
				cause |= (T_ADDR_ERR_LD << CAUSEB_EXCCODE);
				er = EMULATE_PRIV_FAIL;
			}
			break;

		case T_TLB_ST_MISS:
			/* We we are accessing Guest kernel space, then send an address error exception to the guest */
			if (badvaddr >= (unsigned long) KVM_GUEST_KSEG0) {
				printk("%s: ST MISS @ %#lx\n", __func__,
				       badvaddr);
				cause &= ~0xff;
				cause |= (T_ADDR_ERR_ST << CAUSEB_EXCCODE);
				er = EMULATE_PRIV_FAIL;
			}
			break;

		case T_ADDR_ERR_ST:
			printk("%s: address error ST @ %#lx\n", __func__,
			       badvaddr);
			if ((badvaddr & PAGE_MASK) == KVM_GUEST_COMMPAGE_ADDR) {
				cause &= ~0xff;
				cause |= (T_TLB_ST_MISS << CAUSEB_EXCCODE);
			}
			er = EMULATE_PRIV_FAIL;
			break;
		case T_ADDR_ERR_LD:
			printk("%s: address error LD @ %#lx\n", __func__,
			       badvaddr);
			if ((badvaddr & PAGE_MASK) == KVM_GUEST_COMMPAGE_ADDR) {
				cause &= ~0xff;
				cause |= (T_TLB_LD_MISS << CAUSEB_EXCCODE);
			}
			er = EMULATE_PRIV_FAIL;
			break;
		default:
			er = EMULATE_PRIV_FAIL;
			break;
		}
	}

	if (er == EMULATE_PRIV_FAIL) {
		kvm_mips_emulate_exc(cause, opc, run, vcpu);
	}
	return er;
}

/* User Address (UA) fault, this could happen if
 * (1) TLB entry not present/valid in both Guest and shadow host TLBs, in this
 *     case we pass on the fault to the guest kernel and let it handle it.
 * (2) TLB entry is present in the Guest TLB but not in the shadow, in this
 *     case we inject the TLB from the Guest TLB into the shadow host TLB
 */
enum emulation_result
kvm_mips_handle_tlbmiss(unsigned long cause, uint32_t *opc,
			struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	enum emulation_result er = EMULATE_DONE;
	uint32_t exccode = (cause >> CAUSEB_EXCCODE) & 0x1f;
	unsigned long va = vcpu->arch.host_cp0_badvaddr;
	int index;

	kvm_debug("kvm_mips_handle_tlbmiss: badvaddr: %#lx, entryhi: %#lx\n",
		  vcpu->arch.host_cp0_badvaddr, vcpu->arch.host_cp0_entryhi);

	/* KVM would not have got the exception if this entry was valid in the shadow host TLB
	 * Check the Guest TLB, if the entry is not there then send the guest an
	 * exception. The guest exc handler should then inject an entry into the
	 * guest TLB
	 */
	index = kvm_mips_guest_tlb_lookup(vcpu,
					  (va & VPN2_MASK) |
					  (kvm_read_c0_guest_entryhi
					   (vcpu->arch.cop0) & ASID_MASK));
	if (index < 0) {
		if (exccode == T_TLB_LD_MISS) {
			er = kvm_mips_emulate_tlbmiss_ld(cause, opc, run, vcpu);
		} else if (exccode == T_TLB_ST_MISS) {
			er = kvm_mips_emulate_tlbmiss_st(cause, opc, run, vcpu);
		} else {
			printk("%s: invalid exc code: %d\n", __func__, exccode);
			er = EMULATE_FAIL;
		}
	} else {
		struct kvm_mips_tlb *tlb = &vcpu->arch.guest_tlb[index];

		/* Check if the entry is valid, if not then setup a TLB invalid exception to the guest */
		if (!TLB_IS_VALID(*tlb, va)) {
			if (exccode == T_TLB_LD_MISS) {
				er = kvm_mips_emulate_tlbinv_ld(cause, opc, run,
								vcpu);
			} else if (exccode == T_TLB_ST_MISS) {
				er = kvm_mips_emulate_tlbinv_st(cause, opc, run,
								vcpu);
			} else {
				printk("%s: invalid exc code: %d\n", __func__,
				       exccode);
				er = EMULATE_FAIL;
			}
		} else {
#ifdef DEBUG
			kvm_debug
			    ("Injecting hi: %#lx, lo0: %#lx, lo1: %#lx into shadow host TLB\n",
			     tlb->tlb_hi, tlb->tlb_lo0, tlb->tlb_lo1);
#endif
			/* OK we have a Guest TLB entry, now inject it into the shadow host TLB */
			kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb, NULL,
							     NULL);
		}
	}

	return er;
}