linux-kernel - Re: [PATCH] x86/kernel/cpu/amd.c: don't apply the lahf

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Date:   Wed, 12 Jul 2017 15:47:06 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Mikulas Patocka <mpatocka@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/kernel/cpu/amd.c: don't apply the lahf_lm workaround
 in a hypervisor

On Wed, Jul 12, 2017 at 03:19:56AM -0400, Mikulas Patocka wrote:
> When I start a virtual machine, kvm complains about accesses to an unknown
> MSR ("vcpu0 unhandled rdmsr: 0xc001100d"). This is caused by the code in
> init_amd_k8 that tries to work around a BIOS bug that incorrectly sets
> lahf_lm.

No need - there are a lot of qemu configurations which cause the
unhandled MSR warning so no need to pollute the kernel unnecessarily.
The warning is harmless at that.

-- 
Regards/Gruss,
    Boris.

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