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Re: [Qemu-devel] [PATCH] Permit -mem-path without sync mmu
From: |
Avi Kivity |
Subject: |
Re: [Qemu-devel] [PATCH] Permit -mem-path without sync mmu |
Date: |
Mon, 08 Aug 2011 11:24:09 +0300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:5.0) Gecko/20110707 Thunderbird/5.0 |
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