On 08/03/2011 12:24 PM, Xiao Guangrong wrote:
> Maybe it's better to emulate if we can't find a fix for that. > > One way would be to emulate every 20 instructions; this breaks us out of the loop but reduces costly emulations to 5%. > After much thought about this, may be this optimization is not good since: - it is little complex - this optimization is only applied to the instruction emulation caused by #PF - it does not improve too much: if we emulate the instruction, we need to do: - decode instruction - emulate it - zap shadow pages And do this, it can return to the guest, the guest can run the next instruction if we retry the instruction, we need to do: - decode instruction - zap shadow pages then return to the guest and retry the instruction, however, we will get page fault again(since the mapping is still read-only), so we will get another VM-exit and need to do: # trigger page fault - handle the page fault and change the mapping to writable - retry the instruction until now, the guest can run the next instruction So, i do not think the new way is better, your opinion？
We can change to writeable and zap in the same exit, no? Basically call page_fault() again after zapping.
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