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.
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