linux-kernel - Re: [PATCH] KVM: X86: Fix the decoding of segment overrides in 64bit mode

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Message-ID: <9bd82cb0-d88f-4891-a111-3704802e1d4e@redhat.com>
Date:   Thu, 22 Mar 2018 13:38:05 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Andrew Cooper <andrew.cooper3@...rix.com>,
        Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH] KVM: X86: Fix the decoding of segment overrides in 64bit
 mode

On 22/03/2018 12:04, Andrew Cooper wrote:
> We've got a Force Emulation Prefix (ud2a; .ascii "xen") for doing
> magic.  Originally, this was used for PV guests to explicitly request an
> emulated CPUID, but I extended it to HVM guests for "emulate the next
> instruction", after we had some guest user => guest kernel privilege
> escalations because of incorrect emulation.

Wanpeng, why don't you add it behind a new kvm module parameter? :)

Paolo