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SubjectRe: [PATCH v7 3/3] KVM: vmx: handle vm-exit for UMWAIT and TPAUSE
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On 7/13/2019 12:03 AM, Sean Christopherson wrote:
> On Fri, Jul 12, 2019 at 04:29:07PM +0800, Tao Xu wrote:
>> --- a/arch/x86/kvm/vmx/nested.c
>> +++ b/arch/x86/kvm/vmx/nested.c
>> @@ -5213,6 +5213,9 @@ bool nested_vmx_exit_reflected(struct kvm_vcpu *vcpu, u32 exit_reason)
>> case EXIT_REASON_ENCLS:
>> /* SGX is never exposed to L1 */
>> return false;
>> + case EXIT_REASON_UMWAIT: case EXIT_REASON_TPAUSE:
>
> Grouped case statements are usually stacked vertically, e.g.:
>
> case EXIT_REASON_UMWAIT:
> case EXIT_REASON_TPAUSE:
>Ok, thank you for your suggestion.

>> + return nested_cpu_has2(vmcs12,
>> + SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE);
>> default:
>> return true;
>> }
>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>> index 0787f140d155..e026b1313dc3 100644
>> --- a/arch/x86/kvm/vmx/vmx.c
>> +++ b/arch/x86/kvm/vmx/vmx.c
>> @@ -5349,6 +5349,20 @@ static int handle_monitor(struct kvm_vcpu *vcpu)
>> return handle_nop(vcpu);
>> }
>>
>> +static int handle_umwait(struct kvm_vcpu *vcpu)
>> +{
>> + kvm_skip_emulated_instruction(vcpu);
>> + WARN(1, "this should never happen\n");
>
> Blech. I'm guessing this code was copy-pasted from handle_xsaves() and
> handle_xrstors(). The blurb of "this should never happen" isn't very
> helpful, e.g. the WARN itself makes it pretty obvious that we don't expect
> to reach this point. WARN_ONCE would also be preferable, no need to spam
> the log in the event things go completely haywire.
>
> Rather than propagate ugly code, what about defining a common helper, e.g.
>
> static int handle_unexpected_vmexit(struct kvm_vcpu *vcpu)
> {
> kvm_skip_emulated_instruction(vcpu);
> WARN_ONCE(1, "Unexpected VM-Exit = 0x%x", vmcs_read32(VM_EXIT_REASON));
> return 1;
> }
>
> ...
> {
> [EXIT_REASON_XSAVES] = handle_unexpected_vmexit,
> [EXIT_REASON_XRSTORS] = handle_unexpected_vmexit,
>
> [EXIT_REASON_UMWAIT] = handle_unexpected_vmexit,
> [EXIT_REASON_TPAUSE] = handle_unexpected_vmexit,
>
> }
>
Thank you Sean, I will do this in next version of patch.

>> + return 1;
>> +}
>> +
>> +static int handle_tpause(struct kvm_vcpu *vcpu)
>> +{
>> + kvm_skip_emulated_instruction(vcpu);
>> + WARN(1, "this should never happen\n");
>> + return 1;
>> +}
>> +
>> static int handle_invpcid(struct kvm_vcpu *vcpu)
>> {
>> u32 vmx_instruction_info;
>> @@ -5559,6 +5573,8 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
>> [EXIT_REASON_VMFUNC] = handle_vmx_instruction,
>> [EXIT_REASON_PREEMPTION_TIMER] = handle_preemption_timer,
>> [EXIT_REASON_ENCLS] = handle_encls,
>> + [EXIT_REASON_UMWAIT] = handle_umwait,
>> + [EXIT_REASON_TPAUSE] = handle_tpause,
>> };
>>
>> static const int kvm_vmx_max_exit_handlers =
>> --
>> 2.20.1
>>

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