Re: [Qemu-devel] [PATCH 0/3] Vhost: no more leak QEMU virtual addresses to user backend

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 12/21/2017 03:01 PM, Maxime Coquelin wrote:
> 
> 
> On 12/21/2017 04:53 AM, Michael S. Tsirkin wrote:
>> On Wed, Dec 20, 2017 at 04:07:41PM +0000, Stefan Hajnoczi wrote:
>>> On Tue, Dec 19, 2017 at 07:11:26PM +0100, Maxime Coquelin wrote:
>>>> Before this series, QEMU process virtual addresses are sent to the
>>>> user backend as user addresses.
>>>>
>>>> Passing these virtual addresses aren't useful, as the backend doesn't
>>>> direct access to QEMU address space.
>>>>
>>>> It does make sense however for kernel backend, which can access QEMU
>>>> address space.
>>>>
>>>> This series introduce a new enum set by the backend stating whether it
>>>> prefers using QEMU Virtual addresses or Guest physical addresses as
>>>> User address, and make vhost-user backend to use Guest physical
>>>> addresses.
>>>>
>>>> Maxime Coquelin (3):
>>>>    vhost-user: rename VhostUserMemory userspace_addr field to user_addr
>>>>    vhost: introduce backend's user address type
>>>>    vhost-user: no more leak QEMU virtual addresses to user backend
>>>>
>>>>   hw/virtio/vhost-backend.c         |  1 +
>>>>   hw/virtio/vhost-user.c            |  6 ++++--
>>>>   hw/virtio/vhost.c                 | 16 ++++++++++++----
>>>>   include/hw/virtio/vhost-backend.h |  6 ++++++
>>>>   4 files changed, 23 insertions(+), 6 deletions(-)
>>>>
>>>> -- 
>>>> 2.14.3
>>>>
>>>
>>> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
>>
>> This makes make check fail. Any idea why?
>>
> 
> That's interesting, it fails because the rings aren't initialized with
> vhost-user-test (even without my series, but we don't notice).
> 
> It fails in vhost_virtqueue_start(), because vq->desc is NULL.
> 
> Adding some debug prints shows that vq->desc_phys, vq->avail_phys and 
> vq->used_phys are all 0 for both queues.
> 
> So when using QEMU VAs as user addresses, vq->desc, vq->used and
> vq->avail are translated to a non-NULL address, and it doesn't fail.
> 
> Only the multiqueue test returns non-zero and different addresses
> between the rings.
> 
> I'm looking into it.

I get it now, qvirtqueue_setup() is only called in the multiqueue test.

> Regards,
> Maxime