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. Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver") Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx> --- drivers/vfio/pci/vfio_pci_intrs.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c index 237beac83809..136101179fcb 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; -- 2.43.2