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Thu, 05 Nov 2026 11:34:34 -0800 (PST) Received: from stjepan-Aspire-F5-573G.tailc0f20e.ts.net ([2a00:1bb8:118:d39e:452b:db14:9bf:f8a8]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48fea18104bsm12092866f8f.6.2026.11.05.11.34.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Nov 2026 11:34:33 -0800 (PST) From: Stjepan Poljak To: "Michael S. Tsirkin" , Jason Wang Cc: Xuan Zhuo , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , Richard Weinberger , Anton Ivanov , Johannes Berg , Cornelia Huck , Halil Pasic , Eric Farman , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Alexander Graf , virtualization@lists.linux.dev, linux-um@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] virtio_ring: return an error pointer from vring_create_virtqueue() Date: Thu, 5 Nov 2026 20:34:25 +0100 Message-ID: <20261105193426.2999631-1-stjepan.poljak@gmail.com> X-Mailer: git-send-email 2.53.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit vring_create_virtqueue() and vring_create_virtqueue_map() return NULL on any failure, so the error returned from vring_alloc_queue_split() is lost and turned into -ENOMEM. This is especially misleading if vring_alloc_queue_split() rejects a queue size with -EINVAL (i.e. if queue size is not a power of two): virtio_blk virtio0: Bad virtqueue length 100 virtio_blk virtio0: probe with driver virtio_blk failed with error -12 So the error points whoever debugs it at an allocation failure that never happened. Return an ERR_PTR() instead: the error from vring_alloc_queue_split() or vring_alloc_queue_packed(), or -ENOMEM when allocating the virtqueue itself fails. Make the callers, virtio_pci (modern and legacy), virtio_mmio, virtio_vdpa, virtio_ccw and virtio_uml, check with IS_ERR() and pass the error on. The error path in virtio_ccw deletes a non-NULL vq, so clear vq there before taking it. Co-Authored-By: Claude Opus 5.5 Signed-off-by: Stjepan Poljak --- Tested on x86_64 with a virtio-mmio virtio-blk device offering a 100-entry queue: the probe now fails with -22 instead of -12, and a 128-entry queue probes as before. The other transports are only compile-tested (x86_64, ARCH=um, s390 with clang, W=1). No Fixes: tag, since the error has been -ENOMEM since 2010 and nothing regressed. This conflicts trivially with patch 07/12 of Alexander Graf's "virtio: support devices that own their virtqueue memory" v2: https://lore.kernel.org/virtualization/20260818211425.91009-1-graf@amazon.com/ --- arch/um/drivers/virtio_uml.c | 4 ++-- drivers/s390/virtio/virtio_ccw.c | 5 +++-- drivers/virtio/virtio_mmio.c | 4 ++-- drivers/virtio/virtio_pci_legacy.c | 4 ++-- drivers/virtio/virtio_pci_modern.c | 4 ++-- drivers/virtio/virtio_ring.c | 12 +++++++----- drivers/virtio/virtio_vdpa.c | 4 ++-- include/linux/virtio_ring.h | 6 +++++- 8 files changed, 25 insertions(+), 18 deletions(-) diff --git a/arch/um/drivers/virtio_uml.c b/arch/um/drivers/virtio_uml.c index 881c34098a74..8b645523277f 100644 --- a/arch/um/drivers/virtio_uml.c +++ b/arch/um/drivers/virtio_uml.c @@ -984,8 +984,8 @@ static struct virtqueue *vu_setup_vq(struct virtio_device *vdev, vq = vring_create_virtqueue(index, num, PAGE_SIZE, vdev, true, true, ctx, vu_notify, callback, info->name); - if (!vq) { - rc = -ENOMEM; + if (IS_ERR(vq)) { + rc = PTR_ERR(vq); goto error_create; } vq->priv = info; diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c index 552d77998012..c5a30f0a2bc2 100644 --- a/drivers/s390/virtio/virtio_ccw.c +++ b/drivers/s390/virtio/virtio_ccw.c @@ -590,10 +590,11 @@ static struct virtqueue *virtio_ccw_setup_vq(struct virtio_device *vdev, vdev, true, may_reduce, ctx, notify, callback, name); - if (!vq) { + if (IS_ERR(vq)) { /* For now, we fail if we can't get the requested size. */ dev_warn(&vcdev->cdev->dev, "no vq\n"); - err = -ENOMEM; + err = PTR_ERR(vq); + vq = NULL; goto out_err; } diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c index e2ec0ec01d67..c403a025006e 100644 --- a/drivers/virtio/virtio_mmio.c +++ b/drivers/virtio/virtio_mmio.c @@ -396,8 +396,8 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned int in /* Create the vring */ vq = vring_create_virtqueue(index, num, VIRTIO_MMIO_VRING_ALIGN, vdev, true, true, ctx, notify, callback, name); - if (!vq) { - err = -ENOMEM; + if (IS_ERR(vq)) { + err = PTR_ERR(vq); goto error_new_virtqueue; } diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c index 8115aa39e01e..9d94fffff344 100644 --- a/drivers/virtio/virtio_pci_legacy.c +++ b/drivers/virtio/virtio_pci_legacy.c @@ -130,8 +130,8 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev, VIRTIO_PCI_VRING_ALIGN, &vp_dev->vdev, true, false, ctx, vp_notify, callback, name); - if (!vq) - return ERR_PTR(-ENOMEM); + if (IS_ERR(vq)) + return vq; vq->num_max = num; diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c index 922e2df027de..28ccb2130e27 100644 --- a/drivers/virtio/virtio_pci_modern.c +++ b/drivers/virtio/virtio_pci_modern.c @@ -720,8 +720,8 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev, SMP_CACHE_BYTES, &vp_dev->vdev, true, true, ctx, notify, callback, name); - if (!vq) - return ERR_PTR(-ENOMEM); + if (IS_ERR(vq)) + return vq; vq->num_max = num; diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index f683a2d6a200..6dd4a7651bde 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -1421,13 +1421,13 @@ static struct virtqueue *vring_create_virtqueue_split( err = vring_alloc_queue_split(&vring_split, vdev, num, vring_align, may_reduce_num, map); if (err) - return NULL; + return ERR_PTR(err); vq = __vring_new_virtqueue_split(index, &vring_split, vdev, weak_barriers, context, notify, callback, name, map); if (!vq) { vring_free_split(&vring_split, vdev, map); - return NULL; + return ERR_PTR(-ENOMEM); } to_vvq(vq)->we_own_ring = true; @@ -2671,15 +2671,17 @@ static struct virtqueue *vring_create_virtqueue_packed( { struct vring_virtqueue_packed vring_packed = {}; struct virtqueue *vq; + int err; - if (vring_alloc_queue_packed(&vring_packed, vdev, num, map)) - return NULL; + err = vring_alloc_queue_packed(&vring_packed, vdev, num, map); + if (err) + return ERR_PTR(err); vq = __vring_new_virtqueue_packed(index, &vring_packed, vdev, weak_barriers, context, notify, callback, name, map); if (!vq) { vring_free_packed(&vring_packed, vdev, map); - return NULL; + return ERR_PTR(-ENOMEM); } to_vvq(vq)->we_own_ring = true; diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c index f9559b6b2e0b..c1b6134b2267 100644 --- a/drivers/virtio/virtio_vdpa.c +++ b/drivers/virtio/virtio_vdpa.c @@ -208,8 +208,8 @@ virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index, vq = vring_create_virtqueue_map(index, max_num, align, vdev, true, may_reduce_num, ctx, notify, callback, name, map); - if (!vq) { - err = -ENOMEM; + if (IS_ERR(vq)) { + err = PTR_ERR(vq); goto error_new_virtqueue; } diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h index c97a12c1cda3..c808ca7e8d58 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h @@ -66,6 +66,9 @@ struct device; * may_reduce_num is set, then this may allocate a smaller ring than * expected. The caller should query virtqueue_get_vring_size to learn * the actual size of the ring. + * + * Returns the virtqueue or an ERR_PTR() on failure: -EINVAL if num is + * not a valid ring size, -ENOMEM if the ring could not be allocated. */ struct virtqueue *vring_create_virtqueue(unsigned int index, unsigned int num, @@ -80,7 +83,8 @@ struct virtqueue *vring_create_virtqueue(unsigned int index, /* * Creates a virtqueue and allocates the descriptor ring with per - * virtqueue mapping operations. + * virtqueue mapping operations. Returns the virtqueue or an ERR_PTR() + * on failure, like vring_create_virtqueue(). */ struct virtqueue *vring_create_virtqueue_map(unsigned int index, unsigned int num, base-commit: 1a577f9402c1780cc1e663f48d5dd54c02051b09 -- 2.53.0