linux-kernel - Re: [PATCH 03/11] KVM: x86: fast emulate repeat string write instructions

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Message-ID: <4E2FD499.2070308@redhat.com>
Date:	Wed, 27 Jul 2011 12:04:25 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 03/11] KVM: x86: fast emulate repeat string write instructions

On 07/26/2011 02:26 PM, Xiao Guangrong wrote:
> We usually use repeat string instructions to clear the page, for example,
> we call memset to clear a page table, stosb is used in this function, and
> repeated for 1024 times, that means we should occupy mmu lock for 1024 times
> and walking shadow page cache for 1024 times, it is terrible
>
> In fact, if it is the repeat string instructions emulated and it is not a
> IO/MMIO access, we can zap all the corresponding shadow pages and return to the
> guest, then the mapping can became writable and directly write the page

Please generalize this to fail emulation on all non-page-table 
instructions when emulating due to a write protected page that we can 
unprotect.

-- 
error compiling committee.c: too many arguments to function

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