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

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Message-ID: <CAPcxDJ5aB131SqXM3S7Etpj_B6AqVcpLJviMsfvFPbUSGjBb_g@mail.gmail.com>
Date:   Fri, 18 Feb 2022 09:39:14 -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 9:16 AM Borislav Petkov <bp@...en8.de> wrote:
>
> On Fri, Feb 18, 2022 at 08:21:36AM -0800, Jue Wang wrote:
> > My concern was that here returns 0 instead the value read from the msr.
>
> You'd walk into that code only if you're doing MCE injections. In that
> case, it won't read or write MSR_IA32_MISC_ENABLE because the injection
> code writes into the injection mce struct only.
>
> So it won't disable fast strings when you manage to inject the exact
> error type which triggers this erratum.
>
> I think that's actually a good thing - you don't want to disable fast
> strings just because you injected a particular MCE type.

Ok, makes good sense.

Thanks Boris!

-Jue
>
>
> --
> Regards/Gruss,
>     Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette