Re: [Qemu-devel] [PATCH 0/2] virtio len fixes for qemu.

[Rusty Russell]

"Michael S. Tsirkin" <address@hidden> writes:
> On Wed, Mar 11, 2015 at 10:06:40PM +1030, Rusty Russell wrote:
>>         Each entry in the ring is a pair: \field{id} indicates the head
>>         entry of the descriptor chain describing the buffer (this
>>         matches an entry placed in the available ring by the guest
>>         earlier), and \field{len} the total of bytes written into the
>>         buffer. The latter is extremely useful for drivers using
>>         untrusted buffers: if you do not know exactly how much has been
>>         written by the device, you usually have to zero the buffer to
>>         ensure no data leakage occurs.
>
> Right so what does this "if you do not know exactly how much has been
> written by the device" mean?

It means "without this feature, you would not know how much has been
written by the device"...

Should probably become a Note:

Cheers,
Rusty.