linux-kernel - Re: [PATCH v3 0/8] vhost: Reset batched descriptors on SET_VRING

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Message-Id: <916e60f8-45fe-5cc1-d5a1-defdcd00d75b@de.ibm.com>
Date:   Wed, 1 Apr 2020 20:44:01 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Eugenio Perez Martin <eperezma@...hat.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        kvm list <kvm@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Cornelia Huck <cohuck@...hat.com>
Subject: Re: [PATCH v3 0/8] vhost: Reset batched descriptors on SET_VRING_BASE
 call



On 01.04.20 20:40, Eugenio Perez Martin wrote:
> On Wed, Apr 1, 2020 at 9:19 AM Christian Borntraeger
> <borntraeger@...ibm.com> wrote:
>>
>> On 31.03.20 21:27, Eugenio Pérez wrote:
>>> Vhost did not reset properly the batched descriptors on SET_VRING_BASE
>>> event. Because of that, is possible to return an invalid descriptor to
>>> the guest.
>>>
>>> This series ammend this, resetting them every time backend changes, and
>>> creates a test to assert correct behavior. To do that, they need to
>>> expose a new function in virtio_ring, virtqueue_reset_free_head, only
>>> on test code.
>>>
>>> Another useful thing would be to check if mutex is properly get in
>>> vq private_data accessors. Not sure if mutex debug code allow that,
>>> similar to C++ unique lock::owns_lock. Not acquiring in the function
>>> because caller code holds the mutex in order to perform more actions.
>>
>>
>>
>>>
>>> v3:
>>> * Rename accesors functions.
>>> * Make scsi and test use the accesors too.
>>>
>>> v2:
>>> * Squashed commits.
>>> * Create vq private_data accesors (mst).
>>>
>>> This is meant to be applied on top of
>>> c4f1c41a6094582903c75c0dcfacb453c959d457 in
>>> git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git.
>>
>>
>> A quick test on s390 looks good.
>>
> 
> Really good to know :).
> 
> Would it be possible to investigate when qemu launches the offending ioctls?

During guest reboot. This is obvious, no?