This is a note to let you know that I've just added the patch titled
vfio/pci: Disable auto-enable of exclusive INTx IRQ
to the 6.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
vfio-pci-disable-auto-enable-of-exclusive-intx-irq.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 144c648a90dcd34b476ca052b2fa3fecbd82e3b9
Author: Alex Williamson <alex.williamson@xxxxxxxxxx>
Date: Fri Mar 8 16:05:22 2024 -0700
vfio/pci: Disable auto-enable of exclusive INTx IRQ
[ Upstream commit fe9a7082684eb059b925c535682e68c34d487d43 ]
Currently for devices requiring masking at the irqchip for INTx, ie.
devices without DisINTx support, the IRQ is enabled in request_irq()
and subsequently disabled as necessary to align with the masked status
flag. This presents a window where the interrupt could fire between
these events, resulting in the IRQ incrementing the disable depth twice.
This would be unrecoverable for a user since the masked flag prevents
nested enables through vfio.
Instead, invert the logic using IRQF_NO_AUTOEN such that exclusive INTx
is never auto-enabled, then unmask as required.
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver")
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240308230557.805580-2-alex.williamson@xxxxxxxxxx
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index 237beac838097..136101179fcbd 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -296,8 +296,15 @@ static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev, int fd)
ctx->trigger = trigger;
+ /*
+ * Devices without DisINTx support require an exclusive interrupt,
+ * IRQ masking is performed at the IRQ chip. The masked status is
+ * protected by vdev->irqlock. Setup the IRQ without auto-enable and
+ * unmask as necessary below under lock. DisINTx is unmodified by
+ * the IRQ configuration and may therefore use auto-enable.
+ */
if (!vdev->pci_2_3)
- irqflags = 0;
+ irqflags = IRQF_NO_AUTOEN;
ret = request_irq(pdev->irq, vfio_intx_handler,
irqflags, ctx->name, vdev);
@@ -308,13 +315,9 @@ static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev, int fd)
return ret;
}
- /*
- * INTx disable will stick across the new irq setup,
- * disable_irq won't.
- */
spin_lock_irqsave(&vdev->irqlock, flags);
- if (!vdev->pci_2_3 && ctx->masked)
- disable_irq_nosync(pdev->irq);
+ if (!vdev->pci_2_3 && !ctx->masked)
+ enable_irq(pdev->irq);
spin_unlock_irqrestore(&vdev->irqlock, flags);
return 0;
