pci_msix_alloc_irq_at() enables an individual MSI-X interrupt to be allocated after MSI-X enabling. Use dynamic MSI-X (if supported by the device) to allocate an interrupt after MSI-X is enabled. An MSI-X interrupt is dynamically allocated at the time a valid eventfd is assigned. This is different behavior from a range provided during MSI-X enabling where interrupts are allocated for the entire range whether a valid eventfd is provided for each interrupt or not. The PCI-MSIX API requires that some number of irqs are allocated for an initial set of vectors when enabling MSI-X on the device. When dynamic MSIX allocation is not supported, the vector table, and thus the allocated irq set can only be resized by disabling and re-enabling MSI-X with a different range. In that case the irq allocation is essentially a cache for configuring vectors within the previously allocated vector range. When dynamic MSI-X allocation is supported, the API still requires some initial set of irqs to be allocated, but also supports allocating and freeing specific irq vectors both within and beyond the initially allocated range. For consistency between modes, as well as to reduce latency and improve reliability of allocations, and also simplicity, this implementation only releases irqs via pci_free_irq_vectors() when either the interrupt mode changes or the device is released. Signed-off-by: Reinette Chatre <reinette.chatre@xxxxxxxxx> Link: https://lore.kernel.org/lkml/20230403211841.0e206b67.alex.williamson@xxxxxxxxxx/ --- Changes since V4: - Treat pci_irq_vector() returning '0' for Linux IRQ number as kernel bug with a WARN. (Kevin) - Move comment about missing vfio_msi_free_irq() to description of vfio_msi_alloc_irq(). (Kevin) - Add comment at vfio_msi_alloc_irq() call that indicates the allocation is maintained until MSI-X disable to explain the absence of its release in error path. (Kevin) Changes since V3: - Remove vfio_msi_free_irq(). (Alex) - Rework changelog. (Alex) Changes since V2: - Move vfio_irq_ctx_free() to earlier in series to support earlier usage. (Alex) - Use consistent terms in changelog: MSI-x changed to MSI-X. - Make dynamic interrupt context creation generic across all MSI/MSI-X interrupts. This resulted in code moving to earlier in series as part of xarray introduction patch. (Alex) - Remove the local allow_dyn_alloc and direct calling of pci_msix_can_alloc_dyn(), use the new vdev->has_dyn_msix introduced earlier instead. (Alex) - Stop tracking new allocations (remove "new_ctx"). (Alex) - Introduce new wrapper that returns Linux interrupt number or dynamically allocate a new interrupt. Wrapper can be used for all interrupt cases. (Alex) - Only free dynamic MSI-X interrupts on MSI-X teardown. (Alex) Changes since RFC V1: - Add pointer to interrupt context as function parameter to vfio_irq_ctx_free(). (Alex) - Initialize new_ctx to false. (Dan Carpenter) - Only support dynamic allocation if device supports it. (Alex) drivers/vfio/pci/vfio_pci_intrs.c | 47 +++++++++++++++++++++++++++---- 1 file changed, 41 insertions(+), 6 deletions(-) diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c index 867327e159c1..cbb4bcbfbf83 100644 --- a/drivers/vfio/pci/vfio_pci_intrs.c +++ b/drivers/vfio/pci/vfio_pci_intrs.c @@ -381,27 +381,55 @@ static int vfio_msi_enable(struct vfio_pci_core_device *vdev, int nvec, bool msi return 0; } +/* + * vfio_msi_alloc_irq() returns the Linux IRQ number of an MSI or MSI-X device + * interrupt vector. If a Linux IRQ number is not available then a new + * interrupt is allocated if dynamic MSI-X is supported. + * + * Where is vfio_msi_free_irq()? Allocated interrupts are maintained, + * essentially forming a cache that subsequent allocations can draw from. + * Interrupts are freed using pci_free_irq_vectors() when MSI/MSI-X is + * disabled. + */ +static int vfio_msi_alloc_irq(struct vfio_pci_core_device *vdev, + unsigned int vector, bool msix) +{ + struct pci_dev *pdev = vdev->pdev; + struct msi_map map; + int irq; + u16 cmd; + + irq = pci_irq_vector(pdev, vector); + if (WARN_ON_ONCE(irq == 0)) + return -EINVAL; + if (irq > 0 || !msix || !vdev->has_dyn_msix) + return irq; + + cmd = vfio_pci_memory_lock_and_enable(vdev); + map = pci_msix_alloc_irq_at(pdev, vector, NULL); + vfio_pci_memory_unlock_and_restore(vdev, cmd); + + return map.index < 0 ? map.index : map.virq; +} + static int vfio_msi_set_vector_signal(struct vfio_pci_core_device *vdev, unsigned int vector, int fd, bool msix) { struct pci_dev *pdev = vdev->pdev; struct vfio_pci_irq_ctx *ctx; struct eventfd_ctx *trigger; - int irq, ret; + int irq = -EINVAL, ret; u16 cmd; - irq = pci_irq_vector(pdev, vector); - if (irq < 0) - return -EINVAL; - ctx = vfio_irq_ctx_get(vdev, vector); if (ctx) { irq_bypass_unregister_producer(&ctx->producer); - + irq = pci_irq_vector(pdev, vector); cmd = vfio_pci_memory_lock_and_enable(vdev); free_irq(irq, ctx->trigger); vfio_pci_memory_unlock_and_restore(vdev, cmd); + /* Interrupt stays allocated, will be freed at MSI-X disable. */ kfree(ctx->name); eventfd_ctx_put(ctx->trigger); vfio_irq_ctx_free(vdev, ctx, vector); @@ -410,6 +438,13 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_core_device *vdev, if (fd < 0) return 0; + if (irq == -EINVAL) { + /* Interrupt stays allocated, will be freed at MSI-X disable. */ + irq = vfio_msi_alloc_irq(vdev, vector, msix); + if (irq < 0) + return irq; + } + ctx = vfio_irq_ctx_alloc(vdev, vector); if (!ctx) return -ENOMEM; -- 2.34.1
