** Changed in: linux (Ubuntu Hirsute)
Status: Confirmed => Fix Committed
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https://bugs.launchpad.net/bugs/1936682
Title:
Fix kernel panic caused by legacy devices on AMD platforms
Status in HWE Next:
New
Status in linux package in Ubuntu:
Confirmed
Status in linux-oem-5.10 package in Ubuntu:
Invalid
Status in linux-oem-5.13 package in Ubuntu:
Invalid
Status in linux source package in Focal:
Won't Fix
Status in linux-oem-5.10 source package in Focal:
Fix Released
Status in linux-oem-5.13 source package in Focal:
Fix Released
Status in linux source package in Hirsute:
Fix Committed
Status in linux-oem-5.10 source package in Hirsute:
Invalid
Status in linux-oem-5.13 source package in Hirsute:
Invalid
Status in linux source package in Impish:
Confirmed
Status in linux-oem-5.10 source package in Impish:
Invalid
Status in linux-oem-5.13 source package in Impish:
Invalid
Bug description:
[Impact]
When a legacy device is only 32bit DMA capable and it's in the same
IOMMU group with iommu_v2 capable devices, the device in question will
be forced to use identity mapping and triggers kernel panic on DMA
operation because it can't do 64bit DMA.
[Fix]
Keep swiotlb enabled so legacy devices can do 64bit DMA. This is also
how Intel and ARM64 platforms deal with legacy devices.
[Test]
Boot an affected system. Kernel panic in Realtek WiFi driver's probe
routine.
After the patch is applied, the system can work normally.
[Where problems could occur]
The default swiotlb uses 64MB memory, so if the system doesn't have any
legacy device, there are 64MB ram less for the system to use.
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