On 11/29/2011 08:01 PM, Avi Kivity wrote: > On 11/29/2011 01:56 PM, Xiao Guangrong wrote: >> On 11/29/2011 07:20 PM, Avi Kivity wrote: >> >> >>> We used to have a bitmap in a shadow page with a bit set for every slot >>> pointed to by the page. If we extend this to non-leaf pages (so, when >>> we set a bit, we propagate it through its parent_ptes list), then we do >>> the following on write fault: >>> >> >> >> Thanks for the detail. >> >> Um, propagating slot bit to parent ptes is little slow, especially, it >> is the overload for no Xwindow guests which is dirty logged only in the >> migration(i guess most linux guests are running on this mode and migration >> is not frequent). No? > > You need to propagate very infrequently. The first pte added to a page > will need to propagate, but the second (if from the same slot, which is > likely) will already have the bit set in the page, so we're assured it's > set in all its parents. > What will happen if a guest page is unmapped or a shadow page is zapped? It should immediately clear the "slot" bit of the shadow page and its parent, it means it should propagate this "clear slot bit" event to all parents, in the case of softmmu. zapping shadow page is frequently, maybe it is unacceptable? It does not like "unsync" bit which can be lazily cleared, because all bits of hierarchy can be cleared when cr3 reload. -- 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
