KVM: VMX: check use I/O bitmap first before unconditional I/O exit
According to Table C-1 of Intel SDM 3C, a VM exit happens on an I/O instruction when
"use I/O bitmaps" VM-execution control was 0 _and_ the "unconditional I/O exiting"
VM-execution control was 1. So we can't just check "unconditional I/O exiting" alone.
This patch was improved by suggestion from Jan Kiszka.
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Zhihui Zhang <zzhsuny@gmail.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 9cc5484..0abf8b7 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6521,11 +6521,8 @@
int size;
u8 b;
- if (nested_cpu_has(vmcs12, CPU_BASED_UNCOND_IO_EXITING))
- return 1;
-
if (!nested_cpu_has(vmcs12, CPU_BASED_USE_IO_BITMAPS))
- return 0;
+ return nested_cpu_has(vmcs12, CPU_BASED_UNCOND_IO_EXITING);
exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
