[PATCH] virtio_pci: do not mutate caller irq_affinity.pre_vectors
From: Xiong Weimin <hidden>
Date: 2026-08-05 03:29:40
Also in:
lkml, stable
Subsystem:
the rest, virtio core · Maintainers:
Linus Torvalds, "Michael S. Tsirkin", Jason Wang
vp_request_msix_vectors() bumps desc->pre_vectors in place to reserve
the virtio config vector. vp_find_vqs() may call it more than once while
retrying MSI-X with different per-vq policies, so the caller's
irq_affinity keeps accumulating and later attempts get the wrong
affinity layout.
Copy the descriptor to a stack local, adjust pre_vectors there, and
pass that to pci_alloc_irq_vectors_affinity().
Fixes: ba74b6f7fcc0 ("virtio_pci: fix cpu affinity support")
Cc: stable@vger.kernel.org
Signed-off-by: Xiong Weimin <redacted>
---
drivers/virtio/virtio_pci_common.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index 164f480b1..9e75fd03e 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c@@ -128,6 +128,7 @@ static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors, { struct virtio_pci_device *vp_dev = to_vp_device(vdev); const char *name = dev_name(&vp_dev->vdev.dev); + struct irq_affinity tmp_aff, *aff = NULL; unsigned int flags = PCI_IRQ_MSIX; unsigned int i, v; int err = -ENOMEM;
@@ -146,16 +147,19 @@ static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors, GFP_KERNEL)) goto error; - if (!per_vq_vectors) - desc = NULL; - - if (desc) { + if (per_vq_vectors && desc) { + /* + * Do not mutate the caller's irq_affinity across MSI-X + * fallback retries in vp_find_vqs(). + */ + tmp_aff = *desc; + tmp_aff.pre_vectors++; /* virtio config vector */ + aff = &tmp_aff; flags |= PCI_IRQ_AFFINITY; - desc->pre_vectors++; /* virtio config vector */ } err = pci_alloc_irq_vectors_affinity(vp_dev->pci_dev, nvectors, - nvectors, flags, desc); + nvectors, flags, aff); if (err < 0) goto error; vp_dev->msix_enabled = 1;
--
2.43.0