linux-kernel - Re: [PATCH] KVM: x86: Add a helper to dedup reporting of unhandled VM-Exits

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Message-ID: <aQo02LpJ5IfNzVD3@google.com>
Date: Tue, 4 Nov 2025 09:16:08 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Yosry Ahmed <yosry.ahmed@...ux.dev>
Cc: Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: Add a helper to dedup reporting of unhandled VM-Exits

On Mon, Nov 03, 2025, Yosry Ahmed wrote:
> On Thu, Oct 30, 2025 at 11:50:03AM -0700, Sean Christopherson wrote:
> > Add and use a helper, kvm_prepare_unexpected_reason_exit(), to dedup the
> > code that fills the exit reason and CPU when KVM encounters a VM-Exit that
> > KVM doesn't know how to handle.
> > 
> > Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> > ---
> >  arch/x86/include/asm/kvm_host.h |  1 +
> >  arch/x86/kvm/svm/svm.c          |  7 +------
> >  arch/x86/kvm/vmx/tdx.c          |  6 +-----
> >  arch/x86/kvm/vmx/vmx.c          |  9 +--------
> >  arch/x86/kvm/x86.c              | 12 ++++++++++++
> >  5 files changed, 16 insertions(+), 19 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 48598d017d6f..4fbe4b7ce1da 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -2167,6 +2167,7 @@ void __kvm_prepare_emulation_failure_exit(struct kvm_vcpu *vcpu,
> >  void kvm_prepare_emulation_failure_exit(struct kvm_vcpu *vcpu);
> >  
> >  void kvm_prepare_event_vectoring_exit(struct kvm_vcpu *vcpu, gpa_t gpa);
> > +void kvm_prepare_unexpected_reason_exit(struct kvm_vcpu *vcpu, u64 exit_reason);
> >  
> >  void kvm_enable_efer_bits(u64);
> >  bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer);
> > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > index f14709a511aa..83e0d4d5f4c5 100644
> > --- a/arch/x86/kvm/svm/svm.c
> > +++ b/arch/x86/kvm/svm/svm.c
> > @@ -3451,13 +3451,8 @@ static bool svm_check_exit_valid(u64 exit_code)
> >  
> >  static int svm_handle_invalid_exit(struct kvm_vcpu *vcpu, u64 exit_code)
> >  {
> > -	vcpu_unimpl(vcpu, "svm: unexpected exit reason 0x%llx\n", exit_code);
> >  	dump_vmcb(vcpu);
> > -	vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
> > -	vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
> > -	vcpu->run->internal.ndata = 2;
> > -	vcpu->run->internal.data[0] = exit_code;
> > -	vcpu->run->internal.data[1] = vcpu->arch.last_vmentry_cpu;
> > +	kvm_prepare_unexpected_reason_exit(vcpu, exit_code);
> >  	return 0;
> >  }
> 
> We can probably drop svm_handle_invalid_exit() entirely now

Hmm, yeah.  I'll do so in a separate follow-up, as I want to do more than just
fold svm_handle_invalid_exit() into svm_invoke_exit_handler().