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

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Date:	Fri, 10 Jul 2015 17:16:03 +0200
From:	Joerg Roedel <jroedel@...e.de>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	guangrong.xiao@...ux.intel.com, joerg.roedel@...e.de
Subject: Re: [PATCH] KVM: svm: remove KVM_QUIRK_CD_NW_CLEARED quirk

On Fri, Jul 10, 2015 at 02:01:33PM +0200, 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.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/svm.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)

Looks good to me.

Reviewed-by: Joerg Roedel <jroedel@...e.de>

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