[PATCH 3.2 003/140] KVM: x86: Don't re-execute instruction when not passing CR2 value

Ben Hutchings
2018-02-28T15:22:14Z

From: Liran Alon <liran.alon@oracle.com>

commit 9b8ae63798cb97e785a667ff27e43fa6220cb734 upstream.

In case of instruction-decode failure or emulation failure,
x86_emulate_instruction() will call reexecute_instruction() which will
attempt to use the cr2 value passed to x86_emulate_instruction().
However, when x86_emulate_instruction() is called from
emulate_instruction(), cr2 is not passed (passed as 0) and therefore
it doesn't make sense to execute reexecute_instruction() logic at all.

Fixes: 51d8b66199e9 ("KVM: cleanup emulate_instruction")

Signed-off-by: Liran Alon <liran.alon@oracle.com>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/x86/include/asm/kvm_host.h | 3 ++-
arch/x86/kvm/vmx.c | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -701,7 +701,8 @@ int x86_emulate_instruction(struct kvm_v
static inline int emulate_instruction(struct kvm_vcpu *vcpu,
int emulation_type)
{
- return x86_emulate_instruction(vcpu, 0, emulation_type, NULL, 0);
+ return x86_emulate_instruction(vcpu, 0,
+ emulation_type | EMULTYPE_NO_REEXECUTE, NULL, 0);
}

void kvm_enable_efer_bits(u64);
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4891,7 +4891,7 @@ static int handle_invalid_guest_state(st
&& (kvm_get_rflags(&vmx->vcpu) & X86_EFLAGS_IF))
return handle_interrupt_window(&vmx->vcpu);

- err = emulate_instruction(vcpu, EMULTYPE_NO_REEXECUTE);
+ err = emulate_instruction(vcpu, 0);

if (err == EMULATE_DO_MMIO) {
ret = 0;