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462b58fb03
Some devices support ACS functionality even though they don't have a spec-compliant ACS Capability; pci_enable_acs() has a quirk mechanism to handle them. We want to enable ACS whenever possible, but52fbf5bdee("PCI: Cache ACS capability offset in device") inadvertently broke this by calling pci_enable_acs() only if we find an ACS Capability. This resulted in ACS not being enabled for these non-compliant devices, which means devices can't be separated into different IOMMU groups, which in turn means we may not be able to pass those devices through to VMs, as reported by Boris V: https://lore.kernel.org/r/74aeea93-8a46-5f5a-343c-790d4c655da3@bstnet.org Fixes:52fbf5bdee("PCI: Cache ACS capability offset in device") Link: https://lore.kernel.org/r/20201028231545.4116866-1-rajatja@google.com Reported-by: Boris V <borisvk@bstnet.org> Signed-off-by: Rajat Jain <rajatja@google.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
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 Restructured Text 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.