On Mon, Sep 29, 2025 at 03:17:45PM -0600, Alex Williamson wrote:
On Sun, 28 Sep 2025 17:50:18 +0300 Leon Romanovsky leon@kernel.org wrote:
From: Leon Romanovsky leonro@nvidia.com
Make sure that all VFIO PCI devices have peer-to-peer capabilities enables, so we would be able to export their MMIO memory through DMABUF,
Signed-off-by: Leon Romanovsky leonro@nvidia.com
drivers/vfio/pci/vfio_pci_core.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index 7dcf5439dedc..608af135308e 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -28,6 +28,9 @@ #include <linux/nospec.h> #include <linux/sched/mm.h> #include <linux/iommufd.h> +#ifdef CONFIG_VFIO_PCI_DMABUF +#include <linux/pci-p2pdma.h> +#endif #if IS_ENABLED(CONFIG_EEH) #include <asm/eeh.h> #endif @@ -2085,6 +2088,7 @@ int vfio_pci_core_init_dev(struct vfio_device *core_vdev) { struct vfio_pci_core_device *vdev = container_of(core_vdev, struct vfio_pci_core_device, vdev);
- int __maybe_unused ret;
vdev->pdev = to_pci_dev(core_vdev->dev); vdev->irq_type = VFIO_PCI_NUM_IRQS; @@ -2094,6 +2098,11 @@ int vfio_pci_core_init_dev(struct vfio_device *core_vdev) INIT_LIST_HEAD(&vdev->dummy_resources_list); INIT_LIST_HEAD(&vdev->ioeventfds_list); INIT_LIST_HEAD(&vdev->sriov_pfs_item); +#ifdef CONFIG_VFIO_PCI_DMABUF
- ret = pcim_p2pdma_init(vdev->pdev);
- if (ret)
return ret;+#endif init_rwsem(&vdev->memory_lock); xa_init(&vdev->ctx);
What breaks if we don't test the return value and remove all the #ifdefs? The feature call should fail if we don't have a provider but that seems more robust than failing to register the device. Thanks,
pcim_p2pdma_init() fails if memory allocation fails, which is worth to check. Such failure will most likely cause to non-working vfio-pci module anyway, as failure in pcim_p2pdma_init() will trigger OOM. It is better to fail early and help for the system to recover from OOM, instead of delaying to the next failure while trying to load vfio-pci.
CONFIG_VFIO_PCI_DMABUF is mostly for next line "INIT_LIST_HEAD(&vdev->dmabufs);" from the following patch. Because that pcim_p2pdma_init() and dmabufs list are coupled, I put CONFIG_VFIO_PCI_DMABUF on both of them.
Thanks
Alex