Some ATS-capable peripherals can issue requests to the processor to service
peripheral page requests using PCIe PRI (the Page Request Interface). IOMMU
supports PRI using PPR log buffer. IOMMU writes PRI request to PPR log
buffer and sends PPR interrupt to host. When there is no space in the
PPR log buffer (PPR log overflow) it will set PprOverflow bit in 'MMIO
Offset 2020h IOMMU Status Register'. When this happens PPR log needs to be
restarted as specified in IOMMU spec [1] section 2.6.2.
When handling the event it just resumes the PPR log without resizing
(similar to the way event and GA log overflow is handled).
Failing to handle PPR overflow means device may not work properly as
IOMMU stops processing new PPR events from device.
[1] https://www.amd.com/system/files/TechDocs/48882_3.07_PUB.pdf
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Link: https://lore.kernel.org/r/20230628051624.5792-3-vasant.hegde@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
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