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The AMD IOMMU has two modes for generating its own interrupts.
The first is very much based on PCI MSI, and can be configured by Linux
precisely that way. But like legacy unmapped PCI MSI it's limited to
8 bits of APIC ID.
The second method does not use PCI MSI at all in hardawre, and instead
configures the INTCAPXT registers in the IOMMU directly with the APIC ID
and vector.
In the latter case, the IOMMU driver would still use pci_enable_msi(),
read back (through MMIO) the MSI message that Linux wrote to the PCI MSI
table, then swizzle those bits into the appropriate register.
Historically, this worked because__irq_compose_msi_msg() would silently
generate an invalid MSI message with the high bits of the APIC ID in the
high bits of the MSI address. That hack was intended only for the Intel
IOMMU, and I recently enforced that, introducing a warning in
__irq_msi_compose_msg() if it was invoked with an APIC ID above 255.
Fix the AMD IOMMU not to depend on that hack any more, by having its own
irqdomain and directly putting the bits from the irq_cfg into the right
place in its ->activate() method.
Fixes:
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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 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.