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

From: Avi Kivity
Date: Wed Jul 27 2011 - 05:04:36 EST


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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