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From: Rusty Russell <rusty@rustcorp.com.au>
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References: <20121212144758.GF15555@redhat.com> <50C89C47.7040108@redhat.com>
	<20121212152508.GB16750@redhat.com> <50C8A855.4050607@redhat.com>
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	<20121212211926.GA23087@redhat.com> <87bodzrm4z.fsf@codemonkey.ws>
Date: Fri, 14 Dec 2012 11:36:30 +1030
Message-ID: <8738z94f3d.fsf@rustcorp.com.au>
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Subject: Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding
	buffers are flushed
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To: Anthony Liguori <aliguori@us.ibm.com>, "Michael S. Tsirkin" <mst@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

Anthony Liguori <aliguori@us.ibm.com> writes:
> Yes, take a look at the series I sent out that scrubs all of this to
> just send the index and the addresses of the element.
>
> We technically should save the addresses and sizes too.  It makes it a
> heck of a lot safer then re-reading guest memory since we do some
> validation on the size of the sg elements.

Not really.

The guest puts the descriptors in the ring and leaves them there until
the device acks.  If it changes them once they're exposed but before
they're acked, it can get either before or after version, and always
could.

Cheers,
Rusty.