[lkml]   [2012]   [Dec]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 0/7] KVM: Alleviate mmu_lock hold time when we start dirty logging
On Thu, Dec 20, 2012 at 02:02:32PM +0900, Takuya Yoshikawa wrote:
> On Wed, 19 Dec 2012 08:42:57 -0700
> Alex Williamson <> 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?

 \ /
  Last update: 2012-12-20 15:41    [W:0.072 / U:3.260 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site