linux-kernel - Re: [PATCH 0/2] KVM: x86: Convey the exit reason to user-space on emulation failure

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Date:   Wed, 30 Jun 2021 16:33:31 +0000
From:   David Matlack <dmatlack@...gle.com>
To:     David Edmondson <david.edmondson@...cle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Joerg Roedel <joro@...tes.org>, Ingo Molnar <mingo@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>, x86@...nel.org
Subject: Re: [PATCH 0/2] KVM: x86: Convey the exit reason to user-space on
 emulation failure

On Mon, Jun 28, 2021 at 06:31:50PM +0100, David Edmondson wrote:
> To aid in debugging failures in the field, when instruction emulation

What do you mean by a "debugging failure"?

> fails, report the VM exit reason to userspace in order that it can be
> recorded.

What is the benefit of seeing the VM-exit reason that led to an
emulation failure?

> 
> The changes are on top of Aaron's patches from
> https://lore.kernel.org/r/20210510144834.658457-1-aaronlewis@google.com
> which are in the KVM queue, but not yet upstream.
> 
> David Edmondson (2):
>   KVM: x86: Add kvm_x86_ops.get_exit_reason
>   KVM: x86: On emulation failure, convey the exit reason to userspace
> 
>  arch/x86/include/asm/kvm-x86-ops.h |  1 +
>  arch/x86/include/asm/kvm_host.h    |  1 +
>  arch/x86/kvm/svm/svm.c             |  6 ++++++
>  arch/x86/kvm/vmx/vmx.c             |  6 ++++++
>  arch/x86/kvm/x86.c                 | 23 +++++++++++++++++------
>  include/uapi/linux/kvm.h           |  2 ++
>  6 files changed, 33 insertions(+), 6 deletions(-)
> 
> -- 
> 2.30.2
>