From: Avi Kivity <avi@redhat.com>
To: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
KVM list <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 4/6] KVM MMU: optimize for writing cr4
Date: Tue, 13 Apr 2010 09:42:09 +0300 [thread overview]
Message-ID: <4BC41241.30204@redhat.com> (raw)
In-Reply-To: <4BC3DFE3.6090006@cn.fujitsu.com>
On 04/13/2010 06:07 AM, Xiao Guangrong wrote:
>
> And i found the commit 87778d60ee:
>
> | KVM: MMU: Segregate mmu pages created with different cr4.pge settings
> |
> | Don't allow a vcpu with cr4.pge cleared to use a shadow page created with
> | cr4.pge set; this might cause a cr3 switch not to sync ptes that have the
> | global bit set (the global bit has no effect if !cr4.pge).
> |
> | This can only occur on smp with different cr4.pge settings for different
> | vcpus (since a cr4 change will resync the shadow ptes), but there's no
> | cost to being correct here.
>
> In current code, cr3 switch will sync all unsync shadow pages(regardless it's
> global or not) and this issue not live now, so, do we need also revert this
> patch?
>
One path is to revert this patch. The other is to restore the
optimization that relies on it. I'm not sure which is best.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
next prev parent reply other threads:[~2010-04-13 6:42 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-12 7:59 [PATCH 1/6] KVM MMU: remove unused struct Xiao Guangrong
2010-04-12 8:01 ` [PATCH 2/6] KVM MMU: fix kvm_mmu_zap_page() and its calling path Xiao Guangrong
2010-04-12 8:24 ` Avi Kivity
2010-04-12 8:53 ` Xiao Guangrong
2010-04-12 9:08 ` Avi Kivity
2010-04-12 9:22 ` Xiao Guangrong
2010-04-12 10:25 ` Avi Kivity
2010-04-12 12:22 ` Xiao Guangrong
2010-04-12 12:49 ` Avi Kivity
2010-04-12 17:10 ` Marcelo Tosatti
2010-04-13 1:34 ` Xiao Guangrong
2010-04-13 14:59 ` Marcelo Tosatti
2010-04-14 2:14 ` Xiao Guangrong
2010-04-14 16:31 ` Marcelo Tosatti
2010-04-12 8:02 ` [PATCH 3/6] KVM MMU: optimize/cleanup for marking parent unsync Xiao Guangrong
2010-04-12 8:32 ` Avi Kivity
2010-04-12 8:55 ` Xiao Guangrong
2010-04-12 17:12 ` Marcelo Tosatti
2010-04-13 1:53 ` Xiao Guangrong
2010-04-13 11:58 ` Avi Kivity
2010-04-13 15:01 ` Marcelo Tosatti
2010-04-14 3:23 ` Xiao Guangrong
2010-04-14 3:58 ` Xiao Guangrong
2010-04-14 16:35 ` Marcelo Tosatti
2010-04-12 8:03 ` [PATCH 4/6] KVM MMU: optimize for writing cr4 Xiao Guangrong
2010-04-12 8:34 ` Avi Kivity
2010-04-12 10:42 ` Xiao Guangrong
2010-04-12 11:22 ` Avi Kivity
2010-04-13 3:07 ` Xiao Guangrong
2010-04-13 6:42 ` Avi Kivity [this message]
2010-04-12 8:05 ` [PATCH 5/6] KVM MMU: reduce kvm_mmu_page size Xiao Guangrong
2010-04-12 8:36 ` Avi Kivity
2010-04-12 11:11 ` Xiao Guangrong
2010-04-12 8:06 ` [PATCH 6/6] KVM MMU: optimize synchronization shadow pages Xiao Guangrong
2010-04-12 8:43 ` Avi Kivity
2010-04-12 11:14 ` Xiao Guangrong
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