** Changed in: linux (Ubuntu Impish)
Status: Incomplete => Won't Fix
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https://bugs.launchpad.net/bugs/1969086
Title:
Enable swiotlb to avoid untrusted devices errors on AMD platforms
Status in HWE Next:
New
Status in linux package in Ubuntu:
Incomplete
Status in linux-oem-5.14 package in Ubuntu:
Invalid
Status in linux-oem-5.17 package in Ubuntu:
New
Status in linux source package in Focal:
Invalid
Status in linux-oem-5.14 source package in Focal:
New
Status in linux-oem-5.17 source package in Focal:
Invalid
Status in linux source package in Impish:
Won't Fix
Status in linux-oem-5.14 source package in Impish:
Invalid
Status in linux-oem-5.17 source package in Impish:
Invalid
Status in linux source package in Jammy:
Incomplete
Status in linux-oem-5.14 source package in Jammy:
Invalid
Status in linux-oem-5.17 source package in Jammy:
New
Bug description:
It's been observed that plugging in a TBT3 NVME device to a port marked
with ExternalFacingPort that some DMA transactions occur that are not a
full page and so the DMA API attempts to use software bounce buffers
instead of relying upon the IOMMU translation.
This doesn't work and leads to messaging like:
swiotlb buffer is full (sz: 4096 bytes), total 0 (slots), used 0
(slots)
The bounce buffers were originally set up, but torn down during
the boot process.
* This happens because as part of IOMMU initialization
`amd_iommu_init_dma_ops` gets called and resets the global swiotlb to 0.
* When late_init gets called `pci_swiotlb_late_init` `swiotlb_exit` is
called and the buffers are torn down.
This can be observed in the logs:
```
[ 0.407286] AMD-Vi: Extended features (0x246577efa2254afa): PPR NX GT [5]
IA GA PC GA_vAPIC
[ 0.407291] AMD-Vi: Interrupt remapping enabled
[ 0.407292] AMD-Vi: Virtual APIC enabled
[ 0.407872] software IO TLB: tearing down default memory pool
```
This series fixes the behavior of AMD IOMMU to enable swiotlb so that
non-page aligned DMA goes through a bounce buffer.
It also adds a message to help with debugging similar problems in the
future.
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https://bugs.launchpad.net/hwe-next/+bug/1969086/+subscriptions
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