linux-kernel - Re: [PATCH -v2.1] x86/msr: Filter MSR writes

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Message-ID: <20200714154728.GA3101@nazgul.tnic>
Date:   Tue, 14 Jul 2020 17:47:28 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Chris Down <chris@...isdown.name>
Cc:     linux-kernel@...r.kernel.org, sean.j.christopherson@...el.com,
        tony.luck@...el.com, torvalds@...ux-foundation.org, x86@...nel.org,
        kernel-team@...com
Subject: Re: [PATCH -v2.1] x86/msr: Filter MSR writes

On Tue, Jul 14, 2020 at 01:19:55PM +0100, Chris Down wrote:
> That is, even with pr_err_ratelimited, we still end up logging on basically
> every single write, even though it's from the same TGID writing to the same
> MSRs, and end up becoming >80% of kmsg.
> 
> Of course, one can boot with `allow_writes=1` to avoid these messages at

Yes, use that.

>From a quick scan over that "tool" you pointed me at, it pokes at some
MSRs from userspace which the kernel *also* writes to and this is
exactly what should not be allowed.

As to the "MSR hack", please describe what the issue is exactly so that
we can get the proper people involved. If anything, this needs to be
fixed in the kernel properly. If people are waiting for a year for a
BIOS fix, I'd say there's a very slim chance for that to ever happen...

Thx.

-- 
Regards/Gruss,
    Boris.

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