linux-kernel - Re: [PATCH] KVM: X86: Allow userspace to define the microcode version

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Message-ID: <20180226130553.GI4377@pd.tnic>
Date:   Mon, 26 Feb 2018 14:05:54 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Wanpeng Li <kernellwp@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH] KVM: X86: Allow userspace to define the microcode version

On Mon, Feb 26, 2018 at 01:41:38PM +0100, Paolo Bonzini wrote:
> More like "-cpu foo,ucode_rev=0xdeadbeef".  But in practice what would
> happen is one of the following:
> 
> 1) "-cpu host" sets ucode_rev to the same value of the host, everyone
> else leaves it to zero as is now.
> 
> 2) Only Amazon uses this feature and we ignore it. :)

I fear that that might get misused and we probably should consider some
trivial range checking and each qemu cpu model would have a valid range
or so.

Or we should better do that in kvm_set_msr_common directly... although
if we do it here, it would require kvm knowing about all those different
microcode revisions and qemu cpu models sounds better...

-- 
Regards/Gruss,
    Boris.

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