| Message ID | 20210318135223.1342795-2-ckuehl@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | virtiofs: split requests that exceed virtqueue size | expand |
在 2021/3/18 下午9:52, Connor Kuehl 写道: > From section 2.6.5.3.1 (Driver Requirements: Indirect Descriptors) > of the virtio spec: > > "A driver MUST NOT create a descriptor chain longer than the Queue > Size of the device." > > This text suggests that the warning should trigger even if > indirect descriptors are in use. So I think at least the commit log needs some tweak. For split virtqueue. We had: 2.6.5.2 Driver Requirements: The Virtqueue Descriptor Table Drivers MUST NOT add a descriptor chain longer than 2^32 bytes in total; this implies that loops in the descriptor chain are forbidden! 2.6.5.3.1 Driver Requirements: Indirect Descriptors A driver MUST NOT create a descriptor chain longer than the Queue Size of the device. If I understand the spec correctly, the check is only needed for a single indirect descriptor table? For packed virtqueue. We had: 2.7.17 Driver Requirements: Scatter-Gather Support A driver MUST NOT create a descriptor list longer than allowed by the device. A driver MUST NOT create a descriptor list longer than the Queue Size. 2.7.19 Driver Requirements: Indirect Descriptors A driver MUST NOT create a descriptor chain longer than allowed by the device. So it looks to me the packed part is fine. Note that if I understand the spec correctly 2.7.17 implies 2.7.19. Thanks > > Reported-by: Stefan Hajnoczi <stefanha@redhat.com> > Signed-off-by: Connor Kuehl <ckuehl@redhat.com> > --- > drivers/virtio/virtio_ring.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index 71e16b53e9c1..1bc290f9ba13 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -444,11 +444,12 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > head = vq->free_head; > > + WARN_ON_ONCE(total_sg > vq->split.vring.num); > + > if (virtqueue_use_indirect(_vq, total_sg)) > desc = alloc_indirect_split(_vq, total_sg, gfp); > else { > desc = NULL; > - WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect); > } > > if (desc) { > @@ -1118,6 +1119,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > > BUG_ON(total_sg == 0); > > + WARN_ON_ONCE(total_sg > vq->packed.vring.num); > + > if (virtqueue_use_indirect(_vq, total_sg)) > return virtqueue_add_indirect_packed(vq, sgs, total_sg, > out_sgs, in_sgs, data, gfp); > @@ -1125,8 +1128,6 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > head = vq->packed.next_avail_idx; > avail_used_flags = vq->packed.avail_used_flags; > > - WARN_ON_ONCE(total_sg > vq->packed.vring.num && !vq->indirect); > - > desc = vq->packed.vring.desc; > i = head; > descs_used = total_sg;
On Mon, Mar 22, 2021 at 11:22:15AM +0800, Jason Wang wrote: > > 在 2021/3/18 下午9:52, Connor Kuehl 写道: > > From section 2.6.5.3.1 (Driver Requirements: Indirect Descriptors) > > of the virtio spec: > > > > "A driver MUST NOT create a descriptor chain longer than the Queue > > Size of the device." > > > > This text suggests that the warning should trigger even if > > indirect descriptors are in use. > > > So I think at least the commit log needs some tweak. > > For split virtqueue. We had: > > 2.6.5.2 Driver Requirements: The Virtqueue Descriptor Table > > Drivers MUST NOT add a descriptor chain longer than 2^32 bytes in total; > this implies that loops in the descriptor chain are forbidden! > > 2.6.5.3.1 Driver Requirements: Indirect Descriptors > > A driver MUST NOT create a descriptor chain longer than the Queue Size of > the device. > > If I understand the spec correctly, the check is only needed for a single > indirect descriptor table? > > For packed virtqueue. We had: > > 2.7.17 Driver Requirements: Scatter-Gather Support > > A driver MUST NOT create a descriptor list longer than allowed by the > device. > > A driver MUST NOT create a descriptor list longer than the Queue Size. > > 2.7.19 Driver Requirements: Indirect Descriptors > > A driver MUST NOT create a descriptor chain longer than allowed by the > device. > > So it looks to me the packed part is fine. > > Note that if I understand the spec correctly 2.7.17 implies 2.7.19. > > Thanks It would be quite strange for packed and split to differ here: so for packed would you say there's no limit on # of descriptors at all? I am guessing I just forgot to move this part from the format specific to the common part of the spec. This needs discussion in the TC mailing list - want to start a thread there? > > > > > Reported-by: Stefan Hajnoczi <stefanha@redhat.com> > > Signed-off-by: Connor Kuehl <ckuehl@redhat.com> > > --- > > drivers/virtio/virtio_ring.c | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index 71e16b53e9c1..1bc290f9ba13 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -444,11 +444,12 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > head = vq->free_head; > > + WARN_ON_ONCE(total_sg > vq->split.vring.num); > > + > > if (virtqueue_use_indirect(_vq, total_sg)) > > desc = alloc_indirect_split(_vq, total_sg, gfp); > > else { > > desc = NULL; > > - WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect); > > } > > if (desc) { > > @@ -1118,6 +1119,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > > BUG_ON(total_sg == 0); > > + WARN_ON_ONCE(total_sg > vq->packed.vring.num); > > + > > if (virtqueue_use_indirect(_vq, total_sg)) > > return virtqueue_add_indirect_packed(vq, sgs, total_sg, > > out_sgs, in_sgs, data, gfp); > > @@ -1125,8 +1128,6 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > > head = vq->packed.next_avail_idx; > > avail_used_flags = vq->packed.avail_used_flags; > > - WARN_ON_ONCE(total_sg > vq->packed.vring.num && !vq->indirect); > > - > > desc = vq->packed.vring.desc; > > i = head; > > descs_used = total_sg;
在 2021/3/22 下午4:17, Michael S. Tsirkin 写道: > On Mon, Mar 22, 2021 at 11:22:15AM +0800, Jason Wang wrote: >> 在 2021/3/18 下午9:52, Connor Kuehl 写道: >>> From section 2.6.5.3.1 (Driver Requirements: Indirect Descriptors) >>> of the virtio spec: >>> >>> "A driver MUST NOT create a descriptor chain longer than the Queue >>> Size of the device." >>> >>> This text suggests that the warning should trigger even if >>> indirect descriptors are in use. >> >> So I think at least the commit log needs some tweak. >> >> For split virtqueue. We had: >> >> 2.6.5.2 Driver Requirements: The Virtqueue Descriptor Table >> >> Drivers MUST NOT add a descriptor chain longer than 2^32 bytes in total; >> this implies that loops in the descriptor chain are forbidden! >> >> 2.6.5.3.1 Driver Requirements: Indirect Descriptors >> >> A driver MUST NOT create a descriptor chain longer than the Queue Size of >> the device. >> >> If I understand the spec correctly, the check is only needed for a single >> indirect descriptor table? >> >> For packed virtqueue. We had: >> >> 2.7.17 Driver Requirements: Scatter-Gather Support >> >> A driver MUST NOT create a descriptor list longer than allowed by the >> device. >> >> A driver MUST NOT create a descriptor list longer than the Queue Size. >> >> 2.7.19 Driver Requirements: Indirect Descriptors >> >> A driver MUST NOT create a descriptor chain longer than allowed by the >> device. >> >> So it looks to me the packed part is fine. >> >> Note that if I understand the spec correctly 2.7.17 implies 2.7.19. >> >> Thanks > It would be quite strange for packed and split to differ here: > so for packed would you say there's no limit on # of descriptors at all? > > I am guessing I just forgot to move this part from > the format specific to the common part of the spec. > > This needs discussion in the TC mailing list - want to start a thread > there? Will do. Thanks > > > >>> Reported-by: Stefan Hajnoczi <stefanha@redhat.com> >>> Signed-off-by: Connor Kuehl <ckuehl@redhat.com> >>> --- >>> drivers/virtio/virtio_ring.c | 7 ++++--- >>> 1 file changed, 4 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c >>> index 71e16b53e9c1..1bc290f9ba13 100644 >>> --- a/drivers/virtio/virtio_ring.c >>> +++ b/drivers/virtio/virtio_ring.c >>> @@ -444,11 +444,12 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, >>> head = vq->free_head; >>> + WARN_ON_ONCE(total_sg > vq->split.vring.num); >>> + >>> if (virtqueue_use_indirect(_vq, total_sg)) >>> desc = alloc_indirect_split(_vq, total_sg, gfp); >>> else { >>> desc = NULL; >>> - WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect); >>> } >>> if (desc) { >>> @@ -1118,6 +1119,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, >>> BUG_ON(total_sg == 0); >>> + WARN_ON_ONCE(total_sg > vq->packed.vring.num); >>> + >>> if (virtqueue_use_indirect(_vq, total_sg)) >>> return virtqueue_add_indirect_packed(vq, sgs, total_sg, >>> out_sgs, in_sgs, data, gfp); >>> @@ -1125,8 +1128,6 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, >>> head = vq->packed.next_avail_idx; >>> avail_used_flags = vq->packed.avail_used_flags; >>> - WARN_ON_ONCE(total_sg > vq->packed.vring.num && !vq->indirect); >>> - >>> desc = vq->packed.vring.desc; >>> i = head; >>> descs_used = total_sg;
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 71e16b53e9c1..1bc290f9ba13 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -444,11 +444,12 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, head = vq->free_head; + WARN_ON_ONCE(total_sg > vq->split.vring.num); + if (virtqueue_use_indirect(_vq, total_sg)) desc = alloc_indirect_split(_vq, total_sg, gfp); else { desc = NULL; - WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect); } if (desc) { @@ -1118,6 +1119,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, BUG_ON(total_sg == 0); + WARN_ON_ONCE(total_sg > vq->packed.vring.num); + if (virtqueue_use_indirect(_vq, total_sg)) return virtqueue_add_indirect_packed(vq, sgs, total_sg, out_sgs, in_sgs, data, gfp); @@ -1125,8 +1128,6 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, head = vq->packed.next_avail_idx; avail_used_flags = vq->packed.avail_used_flags; - WARN_ON_ONCE(total_sg > vq->packed.vring.num && !vq->indirect); - desc = vq->packed.vring.desc; i = head; descs_used = total_sg;
From section 2.6.5.3.1 (Driver Requirements: Indirect Descriptors) of the virtio spec: "A driver MUST NOT create a descriptor chain longer than the Queue Size of the device." This text suggests that the warning should trigger even if indirect descriptors are in use. Reported-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Connor Kuehl <ckuehl@redhat.com> --- drivers/virtio/virtio_ring.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)