KVM: PPC: booke: standard PPC floating point support

e500mc has a normal PPC FPU, rather than SPE which is found
on e500v1/v2.

Based on code from Liu Yu <yu.liu@freescale.com>.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/powerpc/include/asm/switch_to.h

@@ -17,6 +17,7 @@ extern struct task_struct *_switch(struct thread_struct *prev,
 				   struct thread_struct *next);
 
 extern void giveup_fpu(struct task_struct *);
+extern void load_up_fpu(void);
 extern void disable_kernel_fp(void);
 extern void enable_kernel_fp(void);
 extern void flush_fp_to_thread(struct task_struct *);

arch/powerpc/kvm/booke.c

@@ -457,6 +457,11 @@ void kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
 int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
 {
 	int ret;
+#ifdef CONFIG_PPC_FPU
+	unsigned int fpscr;
+	int fpexc_mode;
+	u64 fpr[32];
+#endif
 
 	if (!vcpu->arch.sane) {
 		kvm_run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
@@ -479,7 +484,46 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
 	}
 
 	kvm_guest_enter();
+
+#ifdef CONFIG_PPC_FPU
+	/* Save userspace FPU state in stack */
+	enable_kernel_fp();
+	memcpy(fpr, current->thread.fpr, sizeof(current->thread.fpr));
+	fpscr = current->thread.fpscr.val;
+	fpexc_mode = current->thread.fpexc_mode;
+
+	/* Restore guest FPU state to thread */
+	memcpy(current->thread.fpr, vcpu->arch.fpr, sizeof(vcpu->arch.fpr));
+	current->thread.fpscr.val = vcpu->arch.fpscr;
+
+	/*
+	 * Since we can't trap on MSR_FP in GS-mode, we consider the guest
+	 * as always using the FPU.  Kernel usage of FP (via
+	 * enable_kernel_fp()) in this thread must not occur while
+	 * vcpu->fpu_active is set.
+	 */
+	vcpu->fpu_active = 1;
+
+	kvmppc_load_guest_fp(vcpu);
+#endif
+
 	ret = __kvmppc_vcpu_run(kvm_run, vcpu);
+
+#ifdef CONFIG_PPC_FPU
+	kvmppc_save_guest_fp(vcpu);
+
+	vcpu->fpu_active = 0;
+
+	/* Save guest FPU state from thread */
+	memcpy(vcpu->arch.fpr, current->thread.fpr, sizeof(vcpu->arch.fpr));
+	vcpu->arch.fpscr = current->thread.fpscr.val;
+
+	/* Restore userspace FPU state from stack */
+	memcpy(current->thread.fpr, fpr, sizeof(current->thread.fpr));
+	current->thread.fpscr.val = fpscr;
+	current->thread.fpexc_mode = fpexc_mode;
+#endif
+
 	kvm_guest_exit();
 
 out:

arch/powerpc/kvm/booke.h

@@ -23,6 +23,7 @@
 #include <linux/types.h>
 #include <linux/kvm_host.h>
 #include <asm/kvm_ppc.h>
+#include <asm/switch_to.h>
 #include "timing.h"
 
 /* interrupt priortity ordering */
@@ -96,4 +97,34 @@ enum int_class {
 
 void kvmppc_set_pending_interrupt(struct kvm_vcpu *vcpu, enum int_class type);
 
+/*
+ * Load up guest vcpu FP state if it's needed.
+ * It also set the MSR_FP in thread so that host know
+ * we're holding FPU, and then host can help to save
+ * guest vcpu FP state if other threads require to use FPU.
+ * This simulates an FP unavailable fault.
+ *
+ * It requires to be called with preemption disabled.
+ */
+static inline void kvmppc_load_guest_fp(struct kvm_vcpu *vcpu)
+{
+#ifdef CONFIG_PPC_FPU
+	if (vcpu->fpu_active && !(current->thread.regs->msr & MSR_FP)) {
+		load_up_fpu();
+		current->thread.regs->msr |= MSR_FP;
+	}
+#endif
+}
+
+/*
+ * Save guest vcpu FP state into thread.
+ * It requires to be called with preemption disabled.
+ */
+static inline void kvmppc_save_guest_fp(struct kvm_vcpu *vcpu)
+{
+#ifdef CONFIG_PPC_FPU
+	if (vcpu->fpu_active && (current->thread.regs->msr & MSR_FP))
+		giveup_fpu(current);
+#endif
+}
 #endif /* __KVM_BOOKE_H__ */