linux-kernel - [PATCH 2/2] vfio/pci: Remove console drivers

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Date:   Mon, 06 Jun 2022 11:53:28 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, airlied@...ux.ie, daniel@...ll.ch
Cc:     Laszlo Ersek <lersek@...hat.com>, Laszlo Ersek <lersek@...hat.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: [PATCH 2/2] vfio/pci: Remove console drivers

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.

Reported-by: Laszlo Ersek <lersek@...hat.com>
Tested-by: Laszlo Ersek <lersek@...hat.com>
Suggested-by: Gerd Hoffmann <kraxel@...hat.com>
Signed-off-by: Alex Williamson <alex.williamson@...hat.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@...hat.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;
+
 	ret = vga_client_register(pdev, vfio_pci_set_decode);
 	if (ret)
 		return ret;