On Thu, Dec 20, 2012 at 10:59:46AM -0200, Marcelo Tosatti wrote: > On Thu, Dec 20, 2012 at 02:02:32PM +0900, Takuya Yoshikawa wrote: > > On Wed, 19 Dec 2012 08:42:57 -0700 > > Alex Williamson <alex.williamson@xxxxxxxxxx> wrote: > > > > > Please let me know if you can identify one of these as the culprit. > > > They're all very simple, but there's always a chance I've missed a hard > > > coding of slot numbers somewhere. Thanks, > > > > I identified the one: > > commit b7f69c555ca430129b6cde81e9f0927531420c5c > > KVM: Minor memory slot optimization > > > > IIUC, the problem was that you did not care about the generation of > > slots which was updated by update_memslots(): > > > > Your patch reused the old memory slots which was there before > > doing the update for invalidating the slot, and badly, we did flush > > shadow pages after that before doing the second update for finally > > installing the new slot. As a result, the generation did not change > > from that of the invalidated one, although the ghc(gfn to hva cache) > > might be stale. > > > > After that, kvm_write_guest_cached() checked if ghc should be > > initialized by comparing ghc's generation with that old one, > > resulting mark_page_dirty_in_slot() was called with the invalid > > cache contents. > > > > Although we can do something to correct the generation alone, I do not > > think such a trick is worth it because this is not a hot path. Let's > > just revert the patch. > > Agreed. No dependencies by the following patches on it? Heh, this generation management looks subtle. Would be easy to break by other changes to the code. I wounder can we make it less subtle somehow. -- Gleb. -- 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
