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Tsirkin" To: Marek Szyprowski Cc: Max Gurtovoy , stefanha@redhat.com, virtualization@lists.linux.dev, axboe@kernel.dk, kvm@vger.kernel.org, linux-block@vger.kernel.org, oren@nvidia.com Subject: Re: [PATCH v2] virtio_blk: implement init_hctx MQ operation Message-ID: <20240912025124-mutt-send-email-mst@kernel.org> References: <20240807224129.34237-1-mgurtovoy@nvidia.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Thu, Sep 12, 2024 at 08:46:15AM +0200, Marek Szyprowski wrote: > Dear All, > > On 08.08.2024 00:41, Max Gurtovoy wrote: > > Set the driver data of the hardware context (hctx) to point directly to > > the virtio block queue. This cleanup improves code readability and > > reduces the number of dereferences in the fast path. > > > > Reviewed-by: Stefan Hajnoczi > > Signed-off-by: Max Gurtovoy > > --- > > drivers/block/virtio_blk.c | 42 ++++++++++++++++++++------------------ > > 1 file changed, 22 insertions(+), 20 deletions(-) > > This patch landed in recent linux-next as commit 8d04556131c1 > ("virtio_blk: implement init_hctx MQ operation"). In my tests I found > that it introduces a regression in system suspend/resume operation. From > time to time system crashes during suspend/resume cycle. Reverting this > patch on top of next-20240911 fixes this problem. > > I've even managed to catch a kernel panic log of this problem on QEMU's > ARM64 'virt' machine: > > root@target:~# time rtcwake -s10 -mmem > rtcwake: wakeup from "mem" using /dev/rtc0 at Thu Sep 12 07:11:52 2024 > Unable to handle kernel NULL pointer dereference at virtual address > 0000000000000090 > Mem abort info: >   ESR = 0x0000000096000046 >   EC = 0x25: DABT (current EL), IL = 32 bits >   SET = 0, FnV = 0 >   EA = 0, S1PTW = 0 >   FSC = 0x06: level 2 translation fault > Data abort info: >   ISV = 0, ISS = 0x00000046, ISS2 = 0x00000000 >   CM = 0, WnR = 1, TnD = 0, TagAccess = 0 >   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 > user pgtable: 4k pages, 48-bit VAs, pgdp=0000000046bbb000 > ... > Internal error: Oops: 0000000096000046 [#1] PREEMPT SMP > Modules linked in: bluetooth ecdh_generic ecc rfkill ipv6 > CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0H Not tainted 6.11.0-rc6+ #9024 > Hardware name: linux,dummy-virt (DT) > Workqueue: kblockd blk_mq_requeue_work > pstate: 800000c5 (Nzcv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : virtqueue_add_split+0x458/0x63c > lr : virtqueue_add_split+0x1d0/0x63c > ... > Call trace: >  virtqueue_add_split+0x458/0x63c >  virtqueue_add_sgs+0xc4/0xec >  virtblk_add_req+0x8c/0xf4 >  virtio_queue_rq+0x6c/0x1bc >  blk_mq_dispatch_rq_list+0x21c/0x714 >  __blk_mq_sched_dispatch_requests+0xb4/0x58c >  blk_mq_sched_dispatch_requests+0x30/0x6c >  blk_mq_run_hw_queue+0x14c/0x40c >  blk_mq_run_hw_queues+0x64/0x124 >  blk_mq_requeue_work+0x188/0x1bc >  process_one_work+0x20c/0x608 >  worker_thread+0x238/0x370 >  kthread+0x124/0x128 >  ret_from_fork+0x10/0x20 > Code: f9404282 79401c21 b9004a81 f94047e1 (f8206841) > ---[ end trace 0000000000000000 ]--- > note: kworker/0:0H[9] exited with irqs disabled > note: kworker/0:0H[9] exited with preempt_count 1 > OK I'll drop from next for now, pls try to debug and repost. > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > > index 2351f411fa46..35a7a586f6f5 100644 > > --- a/drivers/block/virtio_blk.c > > +++ b/drivers/block/virtio_blk.c > > @@ -129,14 +129,6 @@ static inline blk_status_t virtblk_result(u8 status) > > } > > } > > > > -static inline struct virtio_blk_vq *get_virtio_blk_vq(struct blk_mq_hw_ctx *hctx) > > -{ > > - struct virtio_blk *vblk = hctx->queue->queuedata; > > - struct virtio_blk_vq *vq = &vblk->vqs[hctx->queue_num]; > > - > > - return vq; > > -} > > - > > static int virtblk_add_req(struct virtqueue *vq, struct virtblk_req *vbr) > > { > > struct scatterlist out_hdr, in_hdr, *sgs[3]; > > @@ -377,8 +369,7 @@ static void virtblk_done(struct virtqueue *vq) > > > > static void virtio_commit_rqs(struct blk_mq_hw_ctx *hctx) > > { > > - struct virtio_blk *vblk = hctx->queue->queuedata; > > - struct virtio_blk_vq *vq = &vblk->vqs[hctx->queue_num]; > > + struct virtio_blk_vq *vq = hctx->driver_data; > > bool kick; > > > > spin_lock_irq(&vq->lock); > > @@ -428,10 +419,10 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx, > > const struct blk_mq_queue_data *bd) > > { > > struct virtio_blk *vblk = hctx->queue->queuedata; > > + struct virtio_blk_vq *vq = hctx->driver_data; > > struct request *req = bd->rq; > > struct virtblk_req *vbr = blk_mq_rq_to_pdu(req); > > unsigned long flags; > > - int qid = hctx->queue_num; > > bool notify = false; > > blk_status_t status; > > int err; > > @@ -440,26 +431,26 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx, > > if (unlikely(status)) > > return status; > > > > - spin_lock_irqsave(&vblk->vqs[qid].lock, flags); > > - err = virtblk_add_req(vblk->vqs[qid].vq, vbr); > > + spin_lock_irqsave(&vq->lock, flags); > > + err = virtblk_add_req(vq->vq, vbr); > > if (err) { > > - virtqueue_kick(vblk->vqs[qid].vq); > > + virtqueue_kick(vq->vq); > > /* Don't stop the queue if -ENOMEM: we may have failed to > > * bounce the buffer due to global resource outage. > > */ > > if (err == -ENOSPC) > > blk_mq_stop_hw_queue(hctx); > > - spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags); > > + spin_unlock_irqrestore(&vq->lock, flags); > > virtblk_unmap_data(req, vbr); > > return virtblk_fail_to_queue(req, err); > > } > > > > - if (bd->last && virtqueue_kick_prepare(vblk->vqs[qid].vq)) > > + if (bd->last && virtqueue_kick_prepare(vq->vq)) > > notify = true; > > - spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags); > > + spin_unlock_irqrestore(&vq->lock, flags); > > > > if (notify) > > - virtqueue_notify(vblk->vqs[qid].vq); > > + virtqueue_notify(vq->vq); > > return BLK_STS_OK; > > } > > > > @@ -504,7 +495,7 @@ static void virtio_queue_rqs(struct request **rqlist) > > struct request *requeue_list = NULL; > > > > rq_list_for_each_safe(rqlist, req, next) { > > - struct virtio_blk_vq *vq = get_virtio_blk_vq(req->mq_hctx); > > + struct virtio_blk_vq *vq = req->mq_hctx->driver_data; > > bool kick; > > > > if (!virtblk_prep_rq_batch(req)) { > > @@ -1164,6 +1155,16 @@ static const struct attribute_group *virtblk_attr_groups[] = { > > NULL, > > }; > > > > +static int virtblk_init_hctx(struct blk_mq_hw_ctx *hctx, void *data, > > + unsigned int hctx_idx) > > +{ > > + struct virtio_blk *vblk = data; > > + struct virtio_blk_vq *vq = &vblk->vqs[hctx_idx]; > > + > > + hctx->driver_data = vq; > > + return 0; > > +} > > + > > static void virtblk_map_queues(struct blk_mq_tag_set *set) > > { > > struct virtio_blk *vblk = set->driver_data; > > @@ -1205,7 +1206,7 @@ static void virtblk_complete_batch(struct io_comp_batch *iob) > > static int virtblk_poll(struct blk_mq_hw_ctx *hctx, struct io_comp_batch *iob) > > { > > struct virtio_blk *vblk = hctx->queue->queuedata; > > - struct virtio_blk_vq *vq = get_virtio_blk_vq(hctx); > > + struct virtio_blk_vq *vq = hctx->driver_data; > > struct virtblk_req *vbr; > > unsigned long flags; > > unsigned int len; > > @@ -1236,6 +1237,7 @@ static const struct blk_mq_ops virtio_mq_ops = { > > .queue_rqs = virtio_queue_rqs, > > .commit_rqs = virtio_commit_rqs, > > .complete = virtblk_request_done, > > + .init_hctx = virtblk_init_hctx, > > .map_queues = virtblk_map_queues, > > .poll = virtblk_poll, > > }; > > Best regards > -- > Marek Szyprowski, PhD > Samsung R&D Institute Poland