From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 03/11] KVM: x86: fast emulate repeat string write instructions Date: Wed, 27 Jul 2011 12:04:25 +0300 Message-ID: <4E2FD499.2070308@redhat.com> References: <4E2EA3DB.7040403@cn.fujitsu.com> <4E2EA476.9070607@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM To: Xiao Guangrong Return-path: In-Reply-To: <4E2EA476.9070607@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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