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

[Michael S. Tsirkin]

On Wed, Mar 11, 2015 at 02:47:47PM +0800, Fam Zheng wrote:
> On Wed, 03/11 07:19, Michael S. Tsirkin wrote:
> > On Wed, Mar 11, 2015 at 04:29:30PM +1030, Rusty Russell wrote:
> > > The virtio 'used' ring describes descriptors which have been used.  It
> > > also says how many bytes have been written to the ring.  For some cases,
> > > this value is ignored by Linux guests, thus errors have not been noticed.
> > > I was working on increasing the checking in Linux when I noticed this
> > > behaviour.
> > > 
> > > The first patch changes the 'len' formal parameter name to 'len_written' 
> > > to
> > > make the API clearer, and adds an assert(). The second fixes block writes.
> > > 
> > > Cheers,
> > > Rusty.
> > > PS.  It's based on MST's virtio-1.0 tree, but should be easily ported.
> > 
> > Thanks, this applies to current master without issues.
> > However, I think  it's best to apply patch 2, then patch 1,
> > to avoid triggering errors when bisecting.
> 
> I'm seeing a make check failure. If this is a false alarm, the test should be
> fixed too.

Yea, I'm also now thinking we need a spec clarification on this one, and
some testing with non linux drivers before jumping to changing hosts and
guests.


> ---
> 
> qemu-system-x86_64: /var/tmp/patchew-test/git/hw/virtio/virtio.c:254: 
> virtqueue_fill: Assertion `len_written <= tot_wlen' failed.
> Broken pipe
> GTester: last random seed: R02Se642bf29179ebe0c4a92eb02cc488dd8
> [vmxnet3][WR][vmxnet3_peer_has_vnet_hdr]: Peer has no virtio extension. Task 
> offloads will be emulated.
> make: *** [check-qtest-x86_64] Error 1