Hi, This is a replacement for these patches posted to set up the VFIO barmap in the DMABUF export path, and add serialisation:
https://lore.kernel.org/kvm/[email protected] Those patches were motivated by the DMABUF export originally missing a call to vfio_pci_core_setup_barmap() and so possibly exporting a range for which resources weren't yet requested. Responses in the thread indicated there wasn't a strong historical reason to require the bar-mapping to be performed on-demand at BAR reference time. It's much simpler to move this to vfio_pci_core_enable(), and that then avoids having to deal with concurrent lazy requests. The first patch requests PCI resources and pci_iomap() of the BARs in vfio_pci_core_enable(), moving this out of vfio_pci_core_setup_barmap(). Some callers relied on vfio_pci_core_setup_barmap() for its ioremap() effect, and other callers use it for its resource-acquiring effect. The function remains in the first patch, containing a cheap check that both these actions have occurred and keeping the same error behaviour. The second patch then removes calls to vfio_pci_core_setup_barmap(), in favour of two small helper functions which make it clearer to distinguish code that needs just the resource (e.g. mmap) and code that needs the iomap as well (e.g. the rdwr routines, or virtio). The third patch adds the resource check to VFIO DMABUF export, which was previously able to export an unrequested resource. Although patch 1 at first appears to fix this by requesting resources at enable time, code using the BAR still needs to check the resource really was acquired. In future we could reconsider performing all the ioremap()s at startup time, since a lot of VFIO users will never access BARs in-kernel and won't need them. Mapping huge BARs will cost some time & memory, and if necessary this could be reduced by doing the ioremap() portion on demand. === Changes === v2: - Don't fail if resources can't be requested or iomapped, even for valid BARs, as this would change the userspace-observable error behaviour. Specifically, if there was an issue with one particular BAR which happened to never be used, then userspace would never encounter an error for it. Track iomap and resource-acquisition status per BAR. - Break out the checks for resource success from those for iomap success, in the form of the two new helpers. - Third patch to add the check to VFIO DMABUF export, because init-time requests can now fail. v1: https://lore.kernel.org/kvm/[email protected]/ Matt Evans (3): vfio/pci: Set up bar resources and maps in vfio_pci_core_enable() vfio/pci: Replace vfio_pci_core_setup_barmap() with checks for resource/map vfio/pci: Check BAR resources before exporting a DMABUF drivers/vfio/pci/nvgrace-gpu/main.c | 8 ++-- drivers/vfio/pci/vfio_pci_core.c | 66 +++++++++++++++++++++++------ drivers/vfio/pci/vfio_pci_dmabuf.c | 6 ++- drivers/vfio/pci/vfio_pci_rdwr.c | 29 +------------ drivers/vfio/pci/virtio/legacy_io.c | 4 +- include/linux/vfio_pci_core.h | 24 ++++++++++- 6 files changed, 88 insertions(+), 49 deletions(-) -- 2.47.3
