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

Avi Kivity
2011-07-27T09:04:25Z

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.

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