KVM: x86 emulator: Don't write-back cpu-state on X86EMUL_INTERCEPTED

This patch prevents the changed CPU state to be written back
when the emulator detected that the instruction was
intercepted by the guest.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

3 files changed, 7 insertions, 0 deletions

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 470ac54ca38d..1dbd0c736cd1 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -331,6 +331,7 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len);
 #define EMULATION_FAILED -1
 #define EMULATION_OK 0
 #define EMULATION_RESTART 1
+#define EMULATION_INTERCEPTED 2
 int x86_emulate_insn(struct x86_emulate_ctxt *ctxt);
 int emulator_task_switch(struct x86_emulate_ctxt *ctxt,
                          u16 tss_selector, int reason,
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index c2260e57450a..a2c31e527a99 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3592,6 +3592,9 @@ writeback:
 done:
         if (rc == X86EMUL_PROPAGATE_FAULT)
                 ctxt->have_exception = true;
+        if (rc == X86EMUL_INTERCEPTED)
+                return EMULATION_INTERCEPTED;
+
         return (rc == X86EMUL_UNHANDLEABLE) ? EMULATION_FAILED : EMULATION_OK;
 
 twobyte_insn:
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 36786bbb4c09..99bed74779d2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4516,6 +4516,9 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
 restart:
         r = x86_emulate_insn(&vcpu->arch.emulate_ctxt);
 
+        if (r == EMULATION_INTERCEPTED)
+                return EMULATE_DONE;
+
         if (r == EMULATION_FAILED) {
                 if (reexecute_instruction(vcpu, cr2))
                         return EMULATE_DONE;