Re: [PATCH 1/7] KVM: VMX: read idt_vectoring_info a bit earlier
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
Re: [PATCH 1/7] KVM: VMX: read idt_vectoring_info a bit earlier
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.
Re: [PATCH 1/7] KVM: VMX: read idt_vectoring_info a bit earlier
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 >
Re: [PATCH 1/7] KVM: VMX: read idt_vectoring_info a bit earlier
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
[PATCH 1/7] KVM: VMX: read idt_vectoring_info a bit earlier
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
---
arch/x86/kvm/vmx/vmx.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
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);
--
2.26.2
