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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 13 Jul 2022 11:40:03 -0700
Message-ID: <CAHk-=wgq1soM4gudypWLVQdYuvJbXn38LtvJMtnLZX+RTypqLg@mail.gmail.com>
Subject: Re: [PATCH 5.15 00/78] 5.15.55-rc1 review
To:     Guenter Roeck <linux@roeck-us.net>,
        Peter Zijlstra <peterz@infradead.org>,
        Borislav Petkov <bp@suse.de>,
        Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Cc:     Naresh Kamboju <naresh.kamboju@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        kvm list <kvm@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        stable <stable@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Shuah Khan <shuah@kernel.org>, patches@kernelci.org,
        lkft-triage@lists.linaro.org, Pavel Machek <pavel@denx.de>,
        Jon Hunter <jonathanh@nvidia.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Sudip Mukherjee <sudipm.mukherjee@gmail.com>,
        Slade Watkins <slade@sladewatkins.com>,
        Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        X86 ML <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        =?UTF-8?B?QWxleCBCZW5uw6ll?= <alex.bennee@linaro.org>,
        Anders Roxell <anders.roxell@linaro.org>
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On Wed, Jul 13, 2022 at 11:33 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> So I think that that is where the "xaddw_ax_dx+8" comes from: some
> code assumes that FASTOP_SIZE is 8, but that xaddw_ax_dx case was
> actually 9 bytes and thus got that "int3 + padding" in the next 8
> bytes.
>
> The whole kvm x86 emulation thing is quite complicated and has lots
> of instruction size #defines and magic.
>
> I'm not familiar enough with it to go "Ahh, it's obviously XYZ", but
> I'm sure PeterZ and Borislav know exactly what's going on.

And I see that Thadeau already figured it out:

  https://lore.kernel.org/all/20220713171241.184026-1-cascardo@canonical.com/

So presumably we need that patch everywhere.

              Linus