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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@vger.kernel.org>
Fixes: 89e1f7d4c6 ("vfio: Add PCI device driver")
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/20240308230557.805580-2-alex.williamson@redhat.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Alex Williamson 2024-03-08 16:05:22 -07:00 committed by Greg Kroah-Hartman
parent fe750e2744
commit 2a4a666c45
1 changed files with 10 additions and 7 deletions
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17
drivers/vfio/pci/vfio_pci_intrs.c
View File

@ -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;