Hi Alex
Am 06.06.22 um 19:53 schrieb Alex Williamson:
Console drivers can create conflicts with PCI resources resulting in userspace getting mmap failures to memory BARs. This is especially evident when trying to re-use the system primary console for userspace drivers. Attempt to remove all nature of conflicting drivers as part of our VGA initialization.
First a dumb question about your use case. You want to assign a PCI graphics card to a virtual machine and need to remove the generic driver from the framebuffer?
Reported-by: Laszlo Ersek lersek@redhat.com Tested-by: Laszlo Ersek lersek@redhat.com Suggested-by: Gerd Hoffmann kraxel@redhat.com Signed-off-by: Alex Williamson alex.williamson@redhat.com
drivers/vfio/pci/vfio_pci_core.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index a0d69ddaf90d..e0cbcbc2aee1 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -13,6 +13,7 @@ #include <linux/device.h> #include <linux/eventfd.h> #include <linux/file.h> +#include <linux/fb.h> #include <linux/interrupt.h> #include <linux/iommu.h> #include <linux/module.h> @@ -29,6 +30,8 @@
#include <linux/vfio_pci_core.h>
+#include <drm/drm_aperture.h>
- #define DRIVER_AUTHOR "Alex Williamson alex.williamson@redhat.com" #define DRIVER_DESC "core driver for VFIO based PCI devices"
@@ -1793,6 +1796,20 @@ static int vfio_pci_vga_init(struct vfio_pci_core_device *vdev) if (!vfio_pci_is_vga(pdev)) return 0;
+#if IS_REACHABLE(CONFIG_DRM)
- drm_aperture_detach_platform_drivers(pdev);
+#endif
+#if IS_REACHABLE(CONFIG_FB)
- ret = remove_conflicting_pci_framebuffers(pdev, vdev->vdev.ops->name);
- if (ret)
return ret;+#endif
- ret = vga_remove_vgacon(pdev);
- if (ret)
return ret;
You shouldn't have to copy any of the implementation of the aperture helpers.
If you call drm_aperture_remove_conflicting_pci_framebuffers() it should work correctly. The only reason why it requires a DRM driver structure as second argument is for the driver's name. [1] And that name is only used for printing an info message. [2]
The plan forward would be to drop patch 1 entirely.
For patch 2, the most trivial workaround is to instanciate struct drm_driver here and set the name field to 'vdev->vdev.ops->name'. In the longer term, the aperture helpers will be moved out of DRM and into a more prominent location. That workaround will be cleaned up then.
Alternatively, drm_aperture_remove_conflicting_pci_framebuffers() could be changed to accept the name string as second argument, but that's quite a bit of churn within the DRM code.
Best regards Thomas
[1] https://elixir.bootlin.com/linux/v5.18.2/source/drivers/gpu/drm/drm_aperture... [2] https://elixir.bootlin.com/linux/v5.18.2/source/drivers/video/fbdev/core/fbm...
ret = vga_client_register(pdev, vfio_pci_set_decode); if (ret) return ret;