[03/15] KVM: x86 emulator: Don't write-back cpu-state on X86EMUL_INTERCEPTED

Commit Message

Joerg Roedel April 4, 2011, 10:39 a.m. UTC

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 <[e-mail]>
---
 arch/x86/include/asm/kvm_emulate.h |    1 +
 arch/x86/kvm/emulate.c             |    3 +++
 arch/x86/kvm/x86.c                 |    3 +++
 3 files changed, 7 insertions(+), 0 deletions(-)

Patch

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 436207e..366de63 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -325,6 +325,7 @@  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 cee6fc1..b05e50d 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3455,6 +3455,9 @@  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 2b4f5b2..11ecee2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4459,6 +4459,9 @@  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;