KVM: x86 emulator: Add new mode of instruction emulation: skip

In the new mode instruction is decoded, but not executed. The EIP
is moved to point after the instruction.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 0e3a7c6..cb306cf 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -562,6 +562,7 @@ enum emulation_result {
 
 #define EMULTYPE_NO_DECODE         (1 << 0)
 #define EMULTYPE_TRAP_UD           (1 << 1)
+#define EMULTYPE_SKIP              (1 << 2)
 int emulate_instruction(struct kvm_vcpu *vcpu, struct kvm_run *run,
                        unsigned long cr2, u16 error_code, int emulation_type);
 void kvm_report_emulation_failure(struct kvm_vcpu *cvpu, const char *context);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b5ac1b7..8beccaa 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2413,6 +2413,11 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
                }
        }
 
+       if (emulation_type & EMULTYPE_SKIP) {
+               kvm_rip_write(vcpu, vcpu->arch.emulate_ctxt.decode.eip);
+               return EMULATE_DONE;
+       }
+
        r = x86_emulate_insn(&vcpu->arch.emulate_ctxt, &emulate_ops);
 
        if (vcpu->arch.pio.string)