On 14.08.24 07:29, Jason Wang wrote:
> On Tue, Aug 13, 2024 at 8:53 PM Dragos Tatulea <dtatulea@xxxxxxxxxx> wrote:
>>
>>
>>
>> On 13.08.24 08:26, Jason Wang wrote:
>>> On Mon, Aug 12, 2024 at 7:22 PM Dragos Tatulea <dtatulea@xxxxxxxxxx> wrote:
>>>>
>>>>
>>>>
>>>> On 12.08.24 08:49, Jason Wang wrote:
>>>>> On Mon, Aug 12, 2024 at 1:47 PM Jason Wang <jasowang@xxxxxxxxxx> wrote:
>>>>>>
>>>>>> On Fri, Aug 9, 2024 at 2:04 AM Dragos Tatulea <dtatulea@xxxxxxxxxx> wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 08.08.24 10:20, Jason Wang wrote:
>>>>>>>> We used to call irq_bypass_unregister_producer() in
>>>>>>>> vhost_vdpa_setup_vq_irq() which is problematic as we don't know if the
>>>>>>>> token pointer is still valid or not.
>>>>>>>>
>>>>>>>> Actually, we use the eventfd_ctx as the token so the life cycle of the
>>>>>>>> token should be bound to the VHOST_SET_VRING_CALL instead of
>>>>>>>> vhost_vdpa_setup_vq_irq() which could be called by set_status().
>>>>>>>>
>>>>>>>> Fixing this by setting up irq bypass producer's token when handling
>>>>>>>> VHOST_SET_VRING_CALL and un-registering the producer before calling
>>>>>>>> vhost_vring_ioctl() to prevent a possible use after free as eventfd
>>>>>>>> could have been released in vhost_vring_ioctl().
>>>>>>>>
>>>>>>>> Fixes: 2cf1ba9a4d15 ("vhost_vdpa: implement IRQ offloading in vhost_vdpa")
>>>>>>>> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
>>>>>>>> ---
>>>>>>>> Note for Dragos: Please check whether this fixes your issue. I
>>>>>>>> slightly test it with vp_vdpa in L2.
>>>>>>>> ---
>>>>>>>> drivers/vhost/vdpa.c | 12 +++++++++---
>>>>>>>> 1 file changed, 9 insertions(+), 3 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>>>>>>>> index e31ec9ebc4ce..388226a48bcc 100644
>>>>>>>> --- a/drivers/vhost/vdpa.c
>>>>>>>> +++ b/drivers/vhost/vdpa.c
>>>>>>>> @@ -209,11 +209,9 @@ static void vhost_vdpa_setup_vq_irq(struct vhost_vdpa *v, u16 qid)
>>>>>>>> if (irq < 0)
>>>>>>>> return;
>>>>>>>>
>>>>>>>> - irq_bypass_unregister_producer(&vq->call_ctx.producer);
>>>>>>>> if (!vq->call_ctx.ctx)
>>>>>>>> return;
>>>>>>>>
>>>>>>>> - vq->call_ctx.producer.token = vq->call_ctx.ctx;
>>>>>>>> vq->call_ctx.producer.irq = irq;
>>>>>>>> ret = irq_bypass_register_producer(&vq->call_ctx.producer);
>>>>>>>> if (unlikely(ret))
>>>>>>>> @@ -709,6 +707,12 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
>>>>>>>> vq->last_avail_idx = vq_state.split.avail_index;
>>>>>>>> }
>>>>>>>> break;
>>>>>>>> + case VHOST_SET_VRING_CALL:
>>>>>>>> + if (vq->call_ctx.ctx) {
>>>>>>>> + vhost_vdpa_unsetup_vq_irq(v, idx);
>>>>>>>> + vq->call_ctx.producer.token = NULL;
>>>>>>>> + }
>>>>>>>> + break;
>>>>>>>> }
>>>>>>>>
>>>>>>>> r = vhost_vring_ioctl(&v->vdev, cmd, argp);
>>>>>>>> @@ -747,13 +751,14 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
>>>>>>>> cb.callback = vhost_vdpa_virtqueue_cb;
>>>>>>>> cb.private = vq;
>>>>>>>> cb.trigger = vq->call_ctx.ctx;
>>>>>>>> + vq->call_ctx.producer.token = vq->call_ctx.ctx;
>>>>>>>> + vhost_vdpa_setup_vq_irq(v, idx);
>>>>>>>> } else {
>>>>>>>> cb.callback = NULL;
>>>>>>>> cb.private = NULL;
>>>>>>>> cb.trigger = NULL;
>>>>>>>> }
>>>>>>>> ops->set_vq_cb(vdpa, idx, &cb);
>>>>>>>> - vhost_vdpa_setup_vq_irq(v, idx);
>>>>>>>> break;
>>>>>>>>
>>>>>>>> case VHOST_SET_VRING_NUM:
>>>>>>>> @@ -1419,6 +1424,7 @@ static int vhost_vdpa_open(struct inode *inode, struct file *filep)
>>>>>>>> for (i = 0; i < nvqs; i++) {
>>>>>>>> vqs[i] = &v->vqs[i];
>>>>>>>> vqs[i]->handle_kick = handle_vq_kick;
>>>>>>>> + vqs[i]->call_ctx.ctx = NULL;
>>>>>>>> }
>>>>>>>> vhost_dev_init(dev, vqs, nvqs, 0, 0, 0, false,
>>>>>>>> vhost_vdpa_process_iotlb_msg);
>>>>>>>
>>>>>>> No more crashes, but now getting a lot of:
>>>>>>> vhost-vdpa-X: vq Y, irq bypass producer (token 00000000a66e28ab) registration fails, ret = -16
>>>>>>>
>>>>>>> ... seems like the irq_bypass_unregister_producer() that was removed
>>>>>>> might still be needed somewhere?
>>>>>>
>>>> My statement above was not quite correct. The error comes from the
>>>> VQ irq being registered twice:
>>>>
>>>> 1) VHOST_SET_VRING_CALL ioctl gets called for vq 0. VQ irq is unregistered
>>>> (vhost_vdpa_unsetup_vq_irq() and re-registered (vhost_vdpa_setup_vq_irq())
>>>> successfully. So far so good.
>>>>
>>>> 2) set status !DRIVER_OK -> DRIVER_OK happens. VQ irq setup is done
>>>> once again (vhost_vdpa_setup_vq_irq()). As the producer unregister
>>>> was removed in this patch, the register will complain because the producer
>>>> token already exists.
>>>
>>> I see. I think it's probably too tricky to try to register/unregister
>>> a producer during set_vring_call if DRIVER_OK is not set.
>>>
>>> Does it work if we only do vhost_vdpa_unsetup/setup_vq_irq() if
>>> DRIVER_OK is set in vhost_vdpa_vring_ioctl() (on top of this patch)?
>>>
>>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>>> index 388226a48bcc..ab441b8ccd2e 100644
>>> --- a/drivers/vhost/vdpa.c
>>> +++ b/drivers/vhost/vdpa.c
>>> @@ -709,7 +709,9 @@ static long vhost_vdpa_vring_ioctl(struct
>>> vhost_vdpa *v, unsigned int cmd,
>>> break;
>>> case VHOST_SET_VRING_CALL:
>>> if (vq->call_ctx.ctx) {
>>> - vhost_vdpa_unsetup_vq_irq(v, idx);
>>> + if (ops->get_status(vdpa) &
>>> + VIRTIO_CONFIG_S_DRIVER_OK)
>>> + vhost_vdpa_unsetup_vq_irq(v, idx);
>>> vq->call_ctx.producer.token = NULL;
>> I was wondering if it's safe to set NULL also for !DRIVER_OK case,
>> but then I noticed that the !DRIVER_OK transition doesn't set .token to
>> NULL so this is actually beneficial. Did I get it right?
>
> Yes, actually the reason is that we use eventfd as the token, so the
> life cycle of the token is tied to eventfd itself. If we don't set the
> token to NULL here the vhost_vring_ioctl() may just release it which
> may lead to a use-after-free. So this patch doesn't set a token during
> DRIVER_OK transition but during SET_VRING_CALL.
>
Ack. Thanks for the explanation.
>>
>>> }
>>> break;
>>> @@ -752,7 +754,9 @@ static long vhost_vdpa_vring_ioctl(struct
>>> vhost_vdpa *v, unsigned int cmd,
>>> cb.private = vq;
>>> cb.trigger = vq->call_ctx.ctx;
>>> vq->call_ctx.producer.token = vq->call_ctx.ctx;
>>> - vhost_vdpa_setup_vq_irq(v, idx);
>>> + if (ops->get_status(vdpa) &
>>> + VIRTIO_CONFIG_S_DRIVER_OK)
>>> + vhost_vdpa_setup_vq_irq(v, idx);
>>> } else {
>>> cb.callback = NULL;
>>> cb.private = NULL;
>>>
>> Yup, this works.
>>
>> I do understand the fix, but I don't fully understand why this is
>> better than setting the .token to NULL in vhost_vdpa_unsetup_vq_irq()
>> and keeping the token logic inside the vhost_vdpa_setup/unsetup_vq_irq()
>> API.
>
> See the above explanation, hope it clarifies things.
>
Yes it does.
>>
>> In any case, if you send this fix:
>> Tested-by: Dragos Tatulea <dtatulea@xxxxxxxxxx>
FWIW:
Reviewed-by: Dragos Tatulea <dtatulea@xxxxxxxxxx>
>
> Thanks
>
>>
>> Thanks,
>> Dragos
>>>>
>>>>
>>>>>> Probably, but I didn't see this when testing vp_vdpa.
>>>>>>
>>>>>> When did you meet those warnings? Is it during the boot or migration?
>>>> During boot, on the first 2 VQs only (so before the QPs are resized).
>>>> Traffic does work though when the VM is booted.
>>>
>>> Right.
>>>
>>>>
>>>>>
>>>>> Btw, it would be helpful to check if mlx5_get_vq_irq() works
>>>>> correctly. I believe it should return an error if the virtqueue
>>>>> interrupt is not allocated. After a glance at the code, it seems not
>>>>> straightforward to me.
>>>>>
>>>> I think we're good on that front:
>>>> mlx5_get_vq_irq() returns EOPNOTSUPP if the vq irq is not allocated.
>>>
>>> Good to know that.
>>>
>>> Thanks
>>>
>>>>
>>>>
>>>> Thanks,
>>>> Dragos
>>>>
>>>
>>
>
