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

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Message-ID: <CALzav=ewuTYiRS57iYkrVCa6T-garkyFh1OygsQWrUgOS993wQ@mail.gmail.com>
Date:   Wed, 30 Jun 2021 10:08:52 -0700
From:   David Matlack <dmatlack@...gle.com>
To:     David Edmondson <david.edmondson@...cle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        kvm list <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 ML <x86@...nel.org>
Subject: Re: [PATCH 0/2] KVM: x86: Convey the exit reason to user-space on
 emulation failure

On Wed, Jun 30, 2021 at 9:33 AM David Matlack <dmatlack@...gle.com> wrote:
>
> 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"?

Oh! Sorry I misread this as "*debugging failures*" rather than
"debugging *failures*". I know what you mean here :-).

>
> > 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
> >