linux-kernel - Re: [PATCH] KVM: svm: remove KVM_QUIRK_CD_NW

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Date:	Sat, 11 Jul 2015 00:04:08 +0800
From:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
To:	Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
CC:	joerg.roedel@...e.de
Subject: Re: [PATCH] KVM: svm: remove KVM_QUIRK_CD_NW_CLEARED quirk



On 07/10/2015 08:01 PM, Paolo Bonzini wrote:
> We can disable CD unconditionally when there is no assigned device.
> KVM now forces guest PAT to all-writeback in that case, so it makes
> sense to also force CR0.CD=0.
>
> When there are assigned devices, emulate cache-disabled operation
> through the page tables.  This behavior is consistent with VMX,
> where CD/NW are not touched by vmentry/vmexit.
>
> Note that buggy firmware that does not clear CD/NW is _seriously_
> old: SeaBIOS for example has been doing it since October 2008.

Reviewed-by: Xiao Guangrong <guangrong.xiao@...ux.intel.com>
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