Re: [Qemu-devel] [PATCH] Permit -mem-path without sync mmu

[Avi Kivity]

On 08/08/2011 09:03 AM, David Gibson wrote:
> Second, if userspace qemu passing hugepages to kvm can cause (host)
> kernel memory corruption, that is clearly a host kernel bug.  So am I
> correct in thinking this is basically just a safety feature if qemu is
> run on a buggy kernel.

Seems so, yes.  2.6.2[456] are exploitable.  We only found out after 
these were all released.

> Presumably this bug was corrected at some
> point?  Is the presence of the SYNC_MMU feature just being used as a
> proxy for "is this kernel recent enough to have the corruption bug
> fixed"?

SYNC_MMU actually fixes the bug.

> In any case this test sure as hell needs a big comment next to it
> explaining this context.

Yes.


> >  Why are mmu notifiers not implemented for PPC again?
>
> It's just not done yet; we're working on it.  (That is, mmu notifiers
> are certainly present on PPC, it's just they're not wired up to kvm,
> yet).

If ppc doesn't have this issue even without SYNC_MMU, we can make the 
check x86 specific.

--
error compiling committee.c: too many arguments to function