On Fri, Apr 06, 2012 at 01:54:52AM +0800, Xiao Guangrong wrote: > Hi Avi, > > Thanks very much for your review! > > Sorry for the delay reply since i was on vacation. > > On 04/01/2012 11:52 PM, Avi Kivity wrote: > > > On 03/29/2012 11:25 AM, Xiao Guangrong wrote: > >> Using PTE_LIST_WRITE_PROTECT bit in rmap store the write-protect status to > >> avoid unnecessary shadow page walking > >> > >> Also if no shadow page is indirect, the page is write-free > >> > >> > >> @@ -2262,6 +2291,9 @@ static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, > >> } > >> if (need_unsync) > >> kvm_unsync_pages(vcpu, gfn); > >> + > >> + *rmap &= ~PTE_LIST_WRITE_PROTECT; > >> + > >> > > > > So what are the rules for PTE_LIST_WRITE_PROTECT? Is is a cache for the > > mmu_need_write_protect? > > > > I'd like to understand it, I guess it can be set while write protection > > is unneeded, and cleared on the next check? > > > > > Yes, it is used as a cache for mmu_need_write_protect. > > When the gfn is protected by sync sp or read-only host page we set this bit, > and it is be cleared when the sp become unsync or host page becomes writable. Wouldnt dropping support for shadow entirely make it much simpler? The idea to handle RO->RW without mmu_lock is very neat, but the complexity with shadow is horrible. -- 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
