Messages in this thread | | | Date | Tue, 19 Aug 2014 11:03:10 +0200 | From | Paolo Bonzini <> | Subject | Re: [PATCH 1/2] KVM: fix cache stale memslot info with correct mmio generation number |
| |
Il 19/08/2014 10:50, Xiao Guangrong ha scritto: > Okay, what confused me it that it seems that the single line patch > is ok to you. :)
No, it was late and I was confused. :)
> Now, do we really need to care the case 2? like David said: > "Sorry I didn't explain myself very well: Since we can get a single wrong > mmio exit no matter what, it has to be handled in userspace. So my point > was, it doesn't really help to fix that one very specific way that it can > happen, because it can just happen in other ways. (E.g. update memslots > occurs after is_noslot_pfn() and before mmio exit)." > > What's your idea? > > > I think if you always treat the low bit as zero in mmio sptes, you can > > do that without losing a bit of the generation. > > What's you did is avoiding cache a invalid generation number into spte, but > actually if we can figure it out when we check mmio access, it's ok. Like the > updated patch i posted should fix it, that way avoids doubly increase the number.
Yes.
> Okay, if you're interested increasing the number doubly, there is the simpler > one:
This wastes a bit in the mmio spte though. My idea is to increase the memslots generation twice, but drop the low bit in the mmio spte.
Paolo
| |