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KVM: VMX: check use I/O bitmap first before unconditional I/O exit

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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>
This commit is contained in:
Zhihui Zhang 2013-12-30 15:56:29 -05:00 committed by Marcelo Tosatti
parent 171800328f
commit 2f0a6397dd
1 changed files with 1 additions and 4 deletions
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5
arch/x86/kvm/vmx.c
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@ -6521,11 +6521,8 @@ static bool nested_vmx_exit_handled_io(struct kvm_vcpu *vcpu,
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);