From: Rusty Russell <rusty@rustcorp.com.au>
To: Hollis Blanchard <hollisb@us.ibm.com>
Cc: Anthony Liguori <anthony@codemonkey.ws>,
"kvm-devel" <kvm@vger.kernel.org>
Subject: Re: [BUG] virtio-pci queue allocation not page-aligned
Date: Wed, 3 Dec 2008 08:35:53 +1030 [thread overview]
Message-ID: <200812030835.54164.rusty@rustcorp.com.au> (raw)
In-Reply-To: <1228244901.8128.13.camel@localhost.localdomain>
On Wednesday 03 December 2008 05:38:21 Hollis Blanchard wrote:
> I just spent a number of hours tracking this one down, and I'm not too
> thrilled about it. vp_find_vq() does the memory allocation for virtio
> PCI rings, and it uses kzalloc() to do it. This is bad because the ring
> memory *must* be page-aligned.
>
> According to Anthony, at the time this code was written, various slab
> allocators were checked and all happened to return page-aligned buffers.
> So how did I hit a problem? I had enabled CONFIG_SLUB_DEBUG_ON while
> investigating an unrelated problem, which offset the address by 64
> bytes.
>
> One option is to add a BUG_ON(addr & ~PAGE_MASK) to vp_find_vq(). That's
> better than nothing, but still stinks.
It's a bug, we fix it. I've complained before, but since there was no
evidence of it actually breaking, I didn't push.
Prepare a patch, I'll try to get it in this release.
Thanks,
Rusty.
next prev parent reply other threads:[~2008-12-02 22:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-02 19:08 [BUG] virtio-pci queue allocation not page-aligned Hollis Blanchard
2008-12-02 19:12 ` Anthony Liguori
2008-12-02 22:05 ` Rusty Russell [this message]
2008-12-02 22:24 ` Hollis Blanchard
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