KVM: emulator: Fix io permission checking for 64bit guest

Current implementation truncates upper 32bit of TR base address during IO
permission bitmap check. The patch fixes this.

Reported-and-tested-by: Francis Moreau <francis.moro@gmail.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/include/asm/kvm_emulate.h

@@ -142,9 +142,9 @@ struct x86_emulate_ops {
 	int (*pio_out_emulated)(int size, unsigned short port, const void *val,
 				unsigned int count, struct kvm_vcpu *vcpu);
 
-	bool (*get_cached_descriptor)(struct desc_struct *desc,
+	bool (*get_cached_descriptor)(struct desc_struct *desc, u32 *base3,
 				      int seg, struct kvm_vcpu *vcpu);
-	void (*set_cached_descriptor)(struct desc_struct *desc,
+	void (*set_cached_descriptor)(struct desc_struct *desc, u32 base3,
 				      int seg, struct kvm_vcpu *vcpu);
 	u16 (*get_segment_selector)(int seg, struct kvm_vcpu *vcpu);
 	void (*set_segment_selector)(u16 sel, int seg, struct kvm_vcpu *vcpu);

arch/x86/kvm/emulate.c

@@ -878,7 +878,8 @@ static void get_descriptor_table_ptr(struct x86_emulate_ctxt *ctxt,
 	if (selector & 1 << 2) {
 		struct desc_struct desc;
 		memset (dt, 0, sizeof *dt);
-		if (!ops->get_cached_descriptor(&desc, VCPU_SREG_LDTR, ctxt->vcpu))
+		if (!ops->get_cached_descriptor(&desc, NULL, VCPU_SREG_LDTR,
+						ctxt->vcpu))
 			return;
 
 		dt->size = desc_limit_scaled(&desc); /* what if limit > 65535? */
@@ -930,6 +931,7 @@ static int write_segment_descriptor(struct x86_emulate_ctxt *ctxt,
 	return ret;
 }
 
+/* Does not support long mode */
 static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
 				   struct x86_emulate_ops *ops,
 				   u16 selector, int seg)
@@ -1041,7 +1043,7 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
 	}
 load:
 	ops->set_segment_selector(selector, seg, ctxt->vcpu);
-	ops->set_cached_descriptor(&seg_desc, seg, ctxt->vcpu);
+	ops->set_cached_descriptor(&seg_desc, 0, seg, ctxt->vcpu);
 	return X86EMUL_CONTINUE;
 exception:
 	emulate_exception(ctxt, err_vec, err_code, true);
@@ -1561,7 +1563,7 @@ setup_syscalls_segments(struct x86_emulate_ctxt *ctxt,
 			struct desc_struct *ss)
 {
 	memset(cs, 0, sizeof(struct desc_struct));
-	ops->get_cached_descriptor(cs, VCPU_SREG_CS, ctxt->vcpu);
+	ops->get_cached_descriptor(cs, NULL, VCPU_SREG_CS, ctxt->vcpu);
 	memset(ss, 0, sizeof(struct desc_struct));
 
 	cs->l = 0;		/* will be adjusted later */
@@ -1608,9 +1610,9 @@ emulate_syscall(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
 		cs.d = 0;
 		cs.l = 1;
 	}
-	ops->set_cached_descriptor(&cs, VCPU_SREG_CS, ctxt->vcpu);
+	ops->set_cached_descriptor(&cs, 0, VCPU_SREG_CS, ctxt->vcpu);
 	ops->set_segment_selector(cs_sel, VCPU_SREG_CS, ctxt->vcpu);
-	ops->set_cached_descriptor(&ss, VCPU_SREG_SS, ctxt->vcpu);
+	ops->set_cached_descriptor(&ss, 0, VCPU_SREG_SS, ctxt->vcpu);
 	ops->set_segment_selector(ss_sel, VCPU_SREG_SS, ctxt->vcpu);
 
 	c->regs[VCPU_REGS_RCX] = c->eip;
@@ -1680,9 +1682,9 @@ emulate_sysenter(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
 		cs.l = 1;
 	}
 
-	ops->set_cached_descriptor(&cs, VCPU_SREG_CS, ctxt->vcpu);
+	ops->set_cached_descriptor(&cs, 0, VCPU_SREG_CS, ctxt->vcpu);
 	ops->set_segment_selector(cs_sel, VCPU_SREG_CS, ctxt->vcpu);
-	ops->set_cached_descriptor(&ss, VCPU_SREG_SS, ctxt->vcpu);
+	ops->set_cached_descriptor(&ss, 0, VCPU_SREG_SS, ctxt->vcpu);
 	ops->set_segment_selector(ss_sel, VCPU_SREG_SS, ctxt->vcpu);
 
 	ops->get_msr(ctxt->vcpu, MSR_IA32_SYSENTER_EIP, &msr_data);
@@ -1737,9 +1739,9 @@ emulate_sysexit(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
 	cs_sel |= SELECTOR_RPL_MASK;
 	ss_sel |= SELECTOR_RPL_MASK;
 
-	ops->set_cached_descriptor(&cs, VCPU_SREG_CS, ctxt->vcpu);
+	ops->set_cached_descriptor(&cs, 0, VCPU_SREG_CS, ctxt->vcpu);
 	ops->set_segment_selector(cs_sel, VCPU_SREG_CS, ctxt->vcpu);
-	ops->set_cached_descriptor(&ss, VCPU_SREG_SS, ctxt->vcpu);
+	ops->set_cached_descriptor(&ss, 0, VCPU_SREG_SS, ctxt->vcpu);
 	ops->set_segment_selector(ss_sel, VCPU_SREG_SS, ctxt->vcpu);
 
 	c->eip = c->regs[VCPU_REGS_RDX];
@@ -1765,24 +1767,29 @@ static bool emulator_io_port_access_allowed(struct x86_emulate_ctxt *ctxt,
 					    u16 port, u16 len)
 {
 	struct desc_struct tr_seg;
+	u32 base3;
 	int r;
 	u16 io_bitmap_ptr;
 	u8 perm, bit_idx = port & 0x7;
 	unsigned mask = (1 << len) - 1;
+	unsigned long base;
 
-	ops->get_cached_descriptor(&tr_seg, VCPU_SREG_TR, ctxt->vcpu);
+	ops->get_cached_descriptor(&tr_seg, &base3, VCPU_SREG_TR, ctxt->vcpu);
 	if (!tr_seg.p)
 		return false;
 	if (desc_limit_scaled(&tr_seg) < 103)
 		return false;
-	r = ops->read_std(get_desc_base(&tr_seg) + 102, &io_bitmap_ptr, 2,
-			  ctxt->vcpu, NULL);
+	base = get_desc_base(&tr_seg);
+#ifdef CONFIG_X86_64
+	base |= ((u64)base3) << 32;
+#endif
+	r = ops->read_std(base + 102, &io_bitmap_ptr, 2, ctxt->vcpu, NULL);
 	if (r != X86EMUL_CONTINUE)
 		return false;
 	if (io_bitmap_ptr + port/8 > desc_limit_scaled(&tr_seg))
 		return false;
-	r = ops->read_std(get_desc_base(&tr_seg) + io_bitmap_ptr + port/8,
-			  &perm, 1, ctxt->vcpu, NULL);
+	r = ops->read_std(base + io_bitmap_ptr + port/8, &perm, 1, ctxt->vcpu,
+			  NULL);
 	if (r != X86EMUL_CONTINUE)
 		return false;
 	if ((perm >> bit_idx) & mask)
@@ -2127,7 +2134,7 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
 	}
 
 	ops->set_cr(0,  ops->get_cr(0, ctxt->vcpu) | X86_CR0_TS, ctxt->vcpu);
-	ops->set_cached_descriptor(&next_tss_desc, VCPU_SREG_TR, ctxt->vcpu);
+	ops->set_cached_descriptor(&next_tss_desc, 0, VCPU_SREG_TR, ctxt->vcpu);
 	ops->set_segment_selector(tss_selector, VCPU_SREG_TR, ctxt->vcpu);
 
 	if (has_error_code) {

arch/x86/kvm/x86.c

@@ -4162,8 +4162,8 @@ static unsigned long emulator_get_cached_segment_base(int seg,
 	return get_segment_base(vcpu, seg);
 }
 
-static bool emulator_get_cached_descriptor(struct desc_struct *desc, int seg,
-					   struct kvm_vcpu *vcpu)
+static bool emulator_get_cached_descriptor(struct desc_struct *desc, u32 *base3,
+					   int seg, struct kvm_vcpu *vcpu)
 {
 	struct kvm_segment var;
 
@@ -4176,6 +4176,10 @@ static bool emulator_get_cached_descriptor(struct desc_struct *desc, int seg,
 		var.limit >>= 12;
 	set_desc_limit(desc, var.limit);
 	set_desc_base(desc, (unsigned long)var.base);
+#ifdef CONFIG_X86_64
+	if (base3)
+		*base3 = var.base >> 32;
+#endif
 	desc->type = var.type;
 	desc->s = var.s;
 	desc->dpl = var.dpl;
@@ -4188,8 +4192,8 @@ static bool emulator_get_cached_descriptor(struct desc_struct *desc, int seg,
 	return true;
 }
 
-static void emulator_set_cached_descriptor(struct desc_struct *desc, int seg,
-					   struct kvm_vcpu *vcpu)
+static void emulator_set_cached_descriptor(struct desc_struct *desc, u32 base3,
+					   int seg, struct kvm_vcpu *vcpu)
 {
 	struct kvm_segment var;
 
@@ -4197,6 +4201,9 @@ static void emulator_set_cached_descriptor(struct desc_struct *desc, int seg,
 	kvm_get_segment(vcpu, &var, seg);
 
 	var.base = get_desc_base(desc);
+#ifdef CONFIG_X86_64
+	var.base |= ((u64)base3) << 32;
+#endif
 	var.limit = get_desc_limit(desc);
 	if (desc->g)
 		var.limit = (var.limit << 12) | 0xfff;