linux-kernel - Re: [PATCH v2] x86/mce: work around an erratum on fast string copy instructions.

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Message-ID: <CAPcxDJ72dMOpbKXxyb__OeMaEyjYSPtsL_ubVsKOuRXefAQ3_w@mail.gmail.com>
Date:   Fri, 18 Feb 2022 08:21:36 -0800
From:   Jue Wang <juew@...gle.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Tony Luck <tony.luck@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH v2] x86/mce: work around an erratum on fast string copy instructions.

On Fri, Feb 18, 2022 at 8:14 AM Borislav Petkov <bp@...en8.de> wrote:
>
> On Fri, Feb 18, 2022 at 08:03:24AM -0800, Jue Wang wrote:
> > Since MSR_IA32_MISC_ENABLE is not a MCA register, I wonder if we want
> > to mix its read/write with the injected MCE code.
> >
> > I was a bit concerned about potential race with mce-inject and the
> > read/write to MSR_IA32_MISC_ENABLE.
>
> It won't inject anything:
>
>                 offset = msr_to_offset(msr);
>                 if (offset < 0)
>                         ret = 0;
>
Thanks.

My concern was that here returns 0 instead the value read from the msr.

Maybe this cannot happen?
>
> Besides, you need to use those routines due to EX_TYPE_{RD,WR}MSR_IN_MCE
>
> --
> Regards/Gruss,
>     Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette