Commit 05f2a68b authored by Matt Evans's avatar Matt Evans Committed by Alex Williamson
Browse files

vfio/pci: Set up BAR resources and maps in vfio_pci_core_enable() 



Previously BAR resource requests and the corresponding pci_iomap()
were performed on-demand and without synchronisation, which was racy.
Rather than add synchronisation, it's simplest to address this by
doing both activities from vfio_pci_core_enable().

The resource allocation and/or pci_iomap() can still fail; their
status is tracked and existing calls to vfio_pci_core_setup_barmap()
will fail in a similar way to before.  This keeps the point of failure
as observed by userspace the same, i.e. failures to request/map unused
BARs are benign.

Fixes: 89e1f7d4 ("vfio: Add PCI device driver")
Signed-off-by: default avatarMatt Evans <mattev@meta.com>
Link: https://lore.kernel.org/r/20260511145829.2993601-2-mattev@meta.com


[ERR_PTR -> IOMEM_ERR_PTR per lkp report]
Signed-off-by: default avatarAlex Williamson <alex@shazbot.org>
parent df733ddc

drivers/vfio/pci/vfio_pci_core.c

+36 −1
Original line number Diff line number Diff line
@@ -482,6 +482,40 @@ static int vfio_pci_core_runtime_resume(struct device *dev) 
}

#endif /* CONFIG_PM */



/*

 * Eager-request BAR resources, and iomap them.  Soft failures are

 * allowed, and consumers must check the barmap before use in order to

 * give compatible user-visible behaviour with the previous on-demand

 * allocation method.

 */

static void vfio_pci_core_map_bars(struct vfio_pci_core_device *vdev)

{

	struct pci_dev *pdev = vdev->pdev;

	int i;



	for (i = 0; i < PCI_STD_NUM_BARS; i++) {

		int bar = i + PCI_STD_RESOURCES;



		vdev->barmap[bar] = IOMEM_ERR_PTR(-ENODEV);



		if (!pci_resource_len(pdev, i))

			continue;



		if (pci_request_selected_regions(pdev, 1 << bar, "vfio")) {

			pci_dbg(pdev, "Failed to reserve region %d\n", bar);

			vdev->barmap[bar] = IOMEM_ERR_PTR(-EBUSY);

			continue;

		}



		vdev->barmap[bar] = pci_iomap(pdev, bar, 0);

		if (!vdev->barmap[bar]) {

			pci_dbg(pdev, "Failed to iomap region %d\n", bar);

			pci_release_selected_regions(pdev, 1 << bar);

			vdev->barmap[bar] = IOMEM_ERR_PTR(-ENOMEM);

		}

	}

}



/*

 * The pci-driver core runtime PM routines always save the device state

 * before going into suspended state. If the device is going into low power
@@ -568,6 +602,7 @@ int vfio_pci_core_enable(struct vfio_pci_core_device *vdev) 
	if (!vfio_vga_disabled() && vfio_pci_is_vga(pdev))

		vdev->has_vga = true;



	vfio_pci_core_map_bars(vdev);



	return 0;
@@ -648,7 +683,7 @@ void vfio_pci_core_disable(struct vfio_pci_core_device *vdev) 


	for (i = 0; i < PCI_STD_NUM_BARS; i++) {

		bar = i + PCI_STD_RESOURCES;

		if (!vdev->barmap[bar])

		if (IS_ERR_OR_NULL(vdev->barmap[bar]))

			continue;

		pci_iounmap(pdev, vdev->barmap[bar]);

		pci_release_selected_regions(pdev, 1 << bar);

drivers/vfio/pci/vfio_pci_rdwr.c

+7 −19
Original line number Diff line number Diff line
@@ -198,27 +198,15 @@ ssize_t vfio_pci_core_do_io_rw(struct vfio_pci_core_device *vdev, bool test_mem, 
}

EXPORT_SYMBOL_GPL(vfio_pci_core_do_io_rw);



/*

 * The barmap is set up in vfio_pci_core_enable().  Callers use this

 * function to check that the BAR resources are requested or that the

 * pci_iomap() was done.

 */

int vfio_pci_core_setup_barmap(struct vfio_pci_core_device *vdev, int bar)

{

	struct pci_dev *pdev = vdev->pdev;

	int ret;

	void __iomem *io;



	if (vdev->barmap[bar])

		return 0;



	ret = pci_request_selected_regions(pdev, 1 << bar, "vfio");

	if (ret)

		return ret;



	io = pci_iomap(pdev, bar, 0);

	if (!io) {

		pci_release_selected_regions(pdev, 1 << bar);

		return -ENOMEM;

	}



	vdev->barmap[bar] = io;



	if (IS_ERR(vdev->barmap[bar]))

		return PTR_ERR(vdev->barmap[bar]);

	return 0;

}

EXPORT_SYMBOL_GPL(vfio_pci_core_setup_barmap);