From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH] KVM: svm: remove KVM_QUIRK_CD_NW_CLEARED quirk Date: Sat, 11 Jul 2015 00:04:08 +0800 Message-ID: <559FECF8.5090205@linux.intel.com> References: <1436529693-9743-1-git-send-email-pbonzini@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: joerg.roedel@suse.de To: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Return-path: Received: from mga09.intel.com ([134.134.136.24]:7449 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932155AbbGJQJC (ORCPT ); Fri, 10 Jul 2015 12:09:02 -0400 In-Reply-To: <1436529693-9743-1-git-send-email-pbonzini@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 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