5dd8b536bb
If another driver for a VGA compatible GPU (that is passthrough'd) locks the VGA resources (by calling vga_get()), then virtio_gpu driver would encounter the following errors and fail to load during probe and initialization: Invalid read at addr 0x7200005014, size 1, region '(null)', reason: rejected Invalid write at addr 0x7200005014, size 1, region '(null)', reason: rejected virtio_gpu virtio0: virtio: device uses modern interface but does not have VIRTIO_F_VERSION_1 virtio_gpu virtio0: probe with driver virtio_gpu failed with error -22 This issue is only seen if virtio-gpu and the other GPU are on different PCI buses, which can happen if the user includes an additional PCIe port and associates the VGA compatible GPU with it while launching Qemu: qemu-system-x86_64... -device virtio-vga,max_outputs=1,xres=1920,yres=1080,blob=true -device pcie-root-port,id=pcie.1,bus=pcie.0,addr=1c.0,slot=1,chassis=1,multifunction=on -device vfio-pci,host=03:00.0,bus=pcie.1,addr=00.0 ... In the above example, the device 03:00.0 is an Intel DG2 card and this issue is seen when both i915 driver and virtio_gpu driver are loading (or initializing) concurrently or when i915 is loaded first. Note that during initalization, i915 driver does the following in intel_vga_reset_io_mem(): vga_get_uninterruptible(pdev, VGA_RSRC_LEGACY_IO); outb(inb(VGA_MIS_R), VGA_MIS_W); vga_put(pdev, VGA_RSRC_LEGACY_IO); Although, virtio-gpu might own the VGA resources initially, the above call (in i915) to vga_get_uninterruptible() would result in these resources being taken away, which means that virtio-gpu would not be able to decode VGA anymore. This happens in __vga_tryget() when it calls pci_set_vga_state(conflict->pdev, false, pci_bits, flags); where pci_bits = PCI_COMMAND_MEMORY | PCI_COMMAND_IO flags = PCI_VGA_STATE_CHANGE_DECODES | PCI_VGA_STATE_CHANGE_BRIDGE Therefore, to solve this issue, virtio-gpu driver needs to call vga_get() whenever it needs to reclaim and access VGA resources, which is during initial probe and setup. After that, a call to vga_put() would release the lock to allow other VGA compatible devices to access these shared VGA resources. Cc: Gerd Hoffmann <kraxel@redhat.com> Cc: Gurchetan Singh <gurchetansingh@chromium.org> Cc: Chia-I Wu <olvaffe@gmail.com> Reported-by: Dmitry Osipenko <dmitry.osipenko@collabora.com> Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20241211064343.550153-1-vivek.kasireddy@intel.com Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com> |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.