KVM: Fix mov cr0 #GP at wrong instruction

On Intel, we call skip_emulated_instruction() even if we injected a #GP,
resulting in the #GP pointing at the wrong address.

Fix by injecting the exception and skipping the instruction at the same place,
so we can do just one or the other.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

4 files changed, 16 insertions, 13 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 91631b8b209..b2370845021 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -597,7 +597,7 @@ int kvm_load_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector, int seg);
 int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int reason,
                     bool has_error_code, u32 error_code);
 
-void kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
+int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
 void kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3);
 void kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
 void kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 2ae0c392329..6d1616d47c5 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -807,7 +807,7 @@ static void init_vmcb(struct vcpu_svm *svm)
          * svm_set_cr0() sets PG and WP and clears NW and CD on save->cr0.
          */
         svm->vcpu.arch.cr0 = X86_CR0_NW | X86_CR0_CD | X86_CR0_ET;
-        kvm_set_cr0(&svm->vcpu, svm->vcpu.arch.cr0);
+        (void)kvm_set_cr0(&svm->vcpu, svm->vcpu.arch.cr0);
 
         save->cr4 = X86_CR4_PAE;
         /* rdx = ?? */
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 864a1b6d155..1baf4b2d98e 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3157,11 +3157,20 @@ vmx_patch_hypercall(struct kvm_vcpu *vcpu, unsigned char *hypercall)
         hypercall[2] = 0xc1;
 }
 
+static void complete_insn_gp(struct kvm_vcpu *vcpu, int err)
+{
+        if (err)
+                kvm_inject_gp(vcpu, 0);
+        else
+                skip_emulated_instruction(vcpu);
+}
+
 static int handle_cr(struct kvm_vcpu *vcpu)
 {
         unsigned long exit_qualification, val;
         int cr;
         int reg;
+        int err;
 
         exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
         cr = exit_qualification & 15;
@@ -3172,8 +3181,8 @@ static int handle_cr(struct kvm_vcpu *vcpu)
                 trace_kvm_cr_write(cr, val);
                 switch (cr) {
                 case 0:
-                        kvm_set_cr0(vcpu, val);
-                        skip_emulated_instruction(vcpu);
+                        err = kvm_set_cr0(vcpu, val);
+                        complete_insn_gp(vcpu, err);
                         return 1;
                 case 3:
                         kvm_set_cr3(vcpu, val);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b5e644701cc..05e9b5dde64 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -425,7 +425,7 @@ out:
         return changed;
 }
 
-static int __kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
+int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 {
         unsigned long old_cr0 = kvm_read_cr0(vcpu);
         unsigned long update_bits = X86_CR0_PG | X86_CR0_WP |
@@ -468,17 +468,11 @@ static int __kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
                 kvm_mmu_reset_context(vcpu);
         return 0;
 }
-
-void kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
-{
-        if (__kvm_set_cr0(vcpu, cr0))
-                kvm_inject_gp(vcpu, 0);
-}
 EXPORT_SYMBOL_GPL(kvm_set_cr0);
 
 void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw)
 {
-        kvm_set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~0x0eul) | (msw & 0x0f));
+        (void)kvm_set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~0x0eul) | (msw & 0x0f));
 }
 EXPORT_SYMBOL_GPL(kvm_lmsw);
 
@@ -3732,7 +3726,7 @@ static int emulator_set_cr(int cr, unsigned long val, struct kvm_vcpu *vcpu)
 
         switch (cr) {
         case 0:
-                res = __kvm_set_cr0(vcpu, mk_cr_64(kvm_read_cr0(vcpu), val));
+                res = kvm_set_cr0(vcpu, mk_cr_64(kvm_read_cr0(vcpu), val));
                 break;
         case 2:
                 vcpu->arch.cr2 = val;