| Message ID | 20210217145718.1217358-2-mlevitsk@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: random nested fixes | expand |
On 17/02/21 15:57, Maxim Levitsky wrote: > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index b3e36dc3f164..e428d69e21c0 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -6921,13 +6921,15 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu) > if (unlikely((u16)vmx->exit_reason.basic == EXIT_REASON_MCE_DURING_VMENTRY)) > kvm_machine_check(); > > + if (likely(!vmx->exit_reason.failed_vmentry)) > + vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD); > + Any reason for the if? Paolo
On Wed, 2021-02-17 at 17:06 +0100, Paolo Bonzini wrote: > On 17/02/21 15:57, Maxim Levitsky wrote: > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > > index b3e36dc3f164..e428d69e21c0 100644 > > --- a/arch/x86/kvm/vmx/vmx.c > > +++ b/arch/x86/kvm/vmx/vmx.c > > @@ -6921,13 +6921,15 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu) > > if (unlikely((u16)vmx->exit_reason.basic == EXIT_REASON_MCE_DURING_VMENTRY)) > > kvm_machine_check(); > > > > + if (likely(!vmx->exit_reason.failed_vmentry)) > > + vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD); > > + > > Any reason for the if? Sean Christopherson asked me to do this to avoid updating idt_vectoring_info on failed VM entry, to keep things as they were logically before this patch. Best regards, Maxim Levitsky > > Paolo >
On Wed, Feb 17, 2021, Maxim Levitsky wrote: > On Wed, 2021-02-17 at 17:06 +0100, Paolo Bonzini wrote: > > On 17/02/21 15:57, Maxim Levitsky wrote: > > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > > > index b3e36dc3f164..e428d69e21c0 100644 > > > --- a/arch/x86/kvm/vmx/vmx.c > > > +++ b/arch/x86/kvm/vmx/vmx.c > > > @@ -6921,13 +6921,15 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu) > > > if (unlikely((u16)vmx->exit_reason.basic == EXIT_REASON_MCE_DURING_VMENTRY)) > > > kvm_machine_check(); > > > > > > + if (likely(!vmx->exit_reason.failed_vmentry)) > > > + vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD); > > > + > > > > Any reason for the if? > > Sean Christopherson asked me to do this to avoid updating idt_vectoring_info on failed > VM entry, to keep things as they were logically before this patch. Ya, specifically because the field isn't valid if VM-Enter fails. I'm also ok with an unconditional VMREAD if we add a comment stating that it's unnecessary if VM-Enter failed, but faster in the common case.
On 17/02/21 17:21, Sean Christopherson wrote: > On Wed, Feb 17, 2021, Maxim Levitsky wrote: >> On Wed, 2021-02-17 at 17:06 +0100, Paolo Bonzini wrote: >>> On 17/02/21 15:57, Maxim Levitsky wrote: >>>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c >>>> index b3e36dc3f164..e428d69e21c0 100644 >>>> --- a/arch/x86/kvm/vmx/vmx.c >>>> +++ b/arch/x86/kvm/vmx/vmx.c >>>> @@ -6921,13 +6921,15 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu) >>>> if (unlikely((u16)vmx->exit_reason.basic == EXIT_REASON_MCE_DURING_VMENTRY)) >>>> kvm_machine_check(); >>>> >>>> + if (likely(!vmx->exit_reason.failed_vmentry)) >>>> + vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD); >>>> + >>> >>> Any reason for the if? >> >> Sean Christopherson asked me to do this to avoid updating idt_vectoring_info on failed >> VM entry, to keep things as they were logically before this patch. > > Ya, specifically because the field isn't valid if VM-Enter fails. I'm also ok > with an unconditional VMREAD if we add a comment stating that it's unnecessary > if VM-Enter failed, but faster in the common case. It's okay, just good to know! Thanks, paolo
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index b3e36dc3f164..e428d69e21c0 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6921,13 +6921,15 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu) if (unlikely((u16)vmx->exit_reason.basic == EXIT_REASON_MCE_DURING_VMENTRY)) kvm_machine_check(); + if (likely(!vmx->exit_reason.failed_vmentry)) + vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD); + trace_kvm_exit(vmx->exit_reason.full, vcpu, KVM_ISA_VMX); if (unlikely(vmx->exit_reason.failed_vmentry)) return EXIT_FASTPATH_NONE; vmx->loaded_vmcs->launched = 1; - vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD); vmx_recover_nmi_blocking(vmx); vmx_complete_interrupts(vmx);
trace_kvm_exit prints this value (using vmx_get_exit_info) so it makes sense to read it before the trace point. Fixes: dcf068da7eb2 ("KVM: VMX: Introduce generic fastpath handler") Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> --- arch/x86/kvm/vmx/vmx.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)