Re: [PATCH v2 03/22] KVM: SVM: immediately inject INTR vmexit

From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: wei.huang2@amd.com, cavery@redhat.com,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Oliver Upton <oupton@google.com>,
	Jim Mattson <jmattson@google.com>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH v2 03/22] KVM: SVM: immediately inject INTR vmexit
Date: Thu, 21 May 2020 14:50:57 +0200	[thread overview]
Message-ID: <87blmhsb7y.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20200424172416.243870-4-pbonzini@redhat.com>

Paolo Bonzini <pbonzini@redhat.com> writes:

> We can immediately leave SVM guest mode in svm_check_nested_events
> now that we have the nested_run_pending mechanism.  This makes
> things easier because we can run the rest of inject_pending_event
> with GIF=0, and KVM will naturally end up requesting the next
> interrupt window.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  arch/x86/kvm/svm/nested.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index e69e60ac1370..266fde240493 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -778,13 +778,13 @@ int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
>  
>  static void nested_svm_intr(struct vcpu_svm *svm)
>  {
> +	trace_kvm_nested_intr_vmexit(svm->vmcb->save.rip);
> +
>  	svm->vmcb->control.exit_code   = SVM_EXIT_INTR;
>  	svm->vmcb->control.exit_info_1 = 0;
>  	svm->vmcb->control.exit_info_2 = 0;
>  
> -	/* nested_svm_vmexit this gets called afterwards from handle_exit */
> -	svm->nested.exit_required = true;
> -	trace_kvm_nested_intr_vmexit(svm->vmcb->save.rip);
> +	nested_svm_vmexit(svm);
>  }
>  
>  static bool nested_exit_on_intr(struct vcpu_svm *svm)

Sorry for reporting this late but I just found out that this commit
breaks Hyper-V 2016 on KVM on SVM completely (always hangs on boot). I
haven't investigated it yet (well, this is Windows, you know...) but
what's usually different about Hyper-V is that unlike KVM/Linux it has
handlers for some hardware interrupts in the guest and not in the
hypervisor.

-- 
Vitaly