Messages in this thread | | | Date | Wed, 03 Aug 2011 12:25:43 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH v2 02/12] KVM: x86: tag the instructions which are used to write page table |
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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.
-- error compiling committee.c: too many arguments to function
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