linux-kernel - Re: [PATCH v2 3/3] KVM: VMX: enable guest access to LMCE related MSRs

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Message-ID: <da441ea3-1adf-13f7-0254-82814d5055aa@redhat.com>
Date:	Mon, 20 Jun 2016 08:55:40 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Eduardo Habkost <ehabkost@...hat.com>, kvm@...r.kernel.org,
	rkrcmar@...hat.com, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Gleb Natapov <gleb@...nel.org>,
	Boris Petkov <bp@...e.de>, Tony Luck <tony.luck@...el.com>,
	Andi Kleen <andi.kleen@...el.com>,
	Ashok Raj <ashok.raj@...el.com>, libvir-list@...hat.com,
	Jiri Denemark <jdenemar@...hat.com>
Subject: Re: [PATCH v2 3/3] KVM: VMX: enable guest access to LMCE related MSRs



On 20/06/2016 03:49, Haozhong Zhang wrote:
> Thanks for the explanation!
> 
> If we disable LMCE in QEMU by default (even for -cpu host), will it
> still be a problem? That is,
> 
> - pc-2.7 can continue to run on old kernels unless users explicitly
>   require LMCE
> 
> - existing libvirt VM configurations can continue to work on pc-2.7
>   because LMCE is not specified in those configurations and are
>   disabled by default (i.e. no requirement for new kernels)
> 
> - existing QEMU configurations/scripts using pc alias can continue to
>   work on pc-27 for the same reason above.

Yes, that would be fine.  "-cpu host" can leave LMCE enabled if
supported by the kernel.

Paolo