linux-kernel - Re: [PATCH 0/2] KVM: x86: Rep string I/O WARN removal and test

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Date:   Thu, 9 Dec 2021 05:48:40 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] KVM: x86: Rep string I/O WARN removal and test

On Mon, Oct 25, 2021, Sean Christopherson wrote:
> Remove a WARN that was added as part of the recent I/O overhaul to play
> nice with SEV-ES string I/O.
> 
> For the record, my FIXME in lieu of a WARN was deliberate, as I suspected
> userspace could trigger a WARN ;-)
> 
> Based on kvm/master, commit 95e16b4792b0 ("KVM: SEV-ES: go over the
> sev_pio_data buffer in multiple passes if needed").
> 
> Sean Christopherson (2):
>   KVM: x86: Don't WARN if userspace mucks with RCX during string I/O
>     exit
>   KVM: selftests: Add test to verify KVM doesn't explode on "bad" I/O
> 
>  arch/x86/kvm/x86.c                            |   9 +-
>  tools/testing/selftests/kvm/.gitignore        |   1 +
>  tools/testing/selftests/kvm/Makefile          |   1 +
>  .../selftests/kvm/x86_64/userspace_io_test.c  | 114 ++++++++++++++++++
>  4 files changed, 123 insertions(+), 2 deletions(-)
>  create mode 100644 tools/testing/selftests/kvm/x86_64/userspace_io_test.c

Ping.  I completely forgot about this too, until I unintentionally ran a
userspace_io_test that was lying around.