From: Avi Kivity <avi@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>,
LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH v2 2/6] KVM: MMU: don't drop spte if overwrite it from W to RO
Date: Thu, 18 Nov 2010 18:41:34 +0200 [thread overview]
Message-ID: <4CE5573E.4050100@redhat.com> (raw)
In-Reply-To: <20101118153240.GE14327@amt.cnet>
On 11/18/2010 05:32 PM, Marcelo Tosatti wrote:
> > >> There is no need to flush on sync_page path since the guest is
> > >> responsible for it.
> > >>
> > >
> > > If we don't, the next rmap_write_protect() will incorrectly decide that
> > > there's no need to flush tlbs.
> > >
> >
> > Maybe it's not a problem if guest can flush all tlbs after overwrite it?
> > Marcelo, what's your comment about this?
>
> It can, but there is no guarantee. Your patch is correct.
We keep tripping on the same problem again and again. spte.w (and
tlb.pte.w) is multiplexed between guest and host, hence we cannot trust
the guest regarding its consistency.
I wish we had a systematic way of dealing with this.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2010-11-18 16:41 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-17 4:10 [PATCH v2 1/6] KVM: MMU: fix forgot flush vcpu tlbs Xiao Guangrong
2010-11-17 4:10 ` [PATCH v2 2/6] KVM: MMU: don't drop spte if overwrite it from W to RO Xiao Guangrong
2010-11-17 15:42 ` Marcelo Tosatti
2010-11-17 15:57 ` Avi Kivity
2010-11-18 7:12 ` Xiao Guangrong
2010-11-18 15:32 ` Marcelo Tosatti
2010-11-18 16:41 ` Avi Kivity [this message]
2010-11-17 4:11 ` [PATCH v2 3/6] KVM: MMU: don't mark spte notrap if reserved bit set Xiao Guangrong
2010-11-17 15:56 ` Marcelo Tosatti
2010-11-17 4:12 ` [PATCH v2 4/6] KVM: MMU: rename 'reset_host_protection' to 'host_writable' Xiao Guangrong
2010-11-17 15:58 ` Marcelo Tosatti
2010-11-17 4:13 ` [PATCH v2 5/6] KVM: MMU: remove 'clear_unsync' parameter Xiao Guangrong
2010-11-17 16:49 ` Marcelo Tosatti
2010-11-18 7:42 ` Xiao Guangrong
2010-11-18 15:43 ` Marcelo Tosatti
2010-11-17 4:13 ` [PATCH v2 6/6] KVM: MMU: cleanup update_pte, pte_prefetch and sync_page functions Xiao Guangrong
2010-11-17 16:55 ` Marcelo Tosatti
2010-11-17 15:29 ` [PATCH v2 1/6] KVM: MMU: fix forgot flush vcpu tlbs Marcelo Tosatti
2010-11-17 16:26 ` Avi Kivity
2010-11-17 17:36 ` Marcelo Tosatti
2010-11-18 7:17 ` Xiao Guangrong
2010-11-18 9:32 ` Avi Kivity
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