On 08/03/2011 05:25 PM, Avi Kivity wrote: > 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. > OK. :-) Um, how about cache the last eip when we do this optimization, if we meet the same eip, we can break out the potential infinite loop? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
