Public bug reported:
[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.
** Affects: hwe-next
Importance: Undecided
Status: New
** Affects: linux (Ubuntu)
Importance: High
Status: Confirmed
** Affects: linux-oem-5.10 (Ubuntu)
Importance: Undecided
Status: Invalid
** Affects: linux-oem-5.13 (Ubuntu)
Importance: Undecided
Status: Invalid
** Affects: linux (Ubuntu Focal)
Importance: Undecided
Status: Won't Fix
** Affects: linux-oem-5.10 (Ubuntu Focal)
Importance: High
Status: Confirmed
** Affects: linux-oem-5.13 (Ubuntu Focal)
Importance: High
Status: Confirmed
** Affects: linux (Ubuntu Hirsute)
Importance: High
Status: Confirmed
** Affects: linux-oem-5.10 (Ubuntu Hirsute)
Importance: Undecided
Status: Invalid
** Affects: linux-oem-5.13 (Ubuntu Hirsute)
Importance: Undecided
Status: Invalid
** Affects: linux (Ubuntu Impish)
Importance: High
Status: Confirmed
** Affects: linux-oem-5.10 (Ubuntu Impish)
Importance: Undecided
Status: Invalid
** Affects: linux-oem-5.13 (Ubuntu Impish)
Importance: Undecided
Status: Invalid
** Tags: oem-priority originate-from-1933798 stella
** Also affects: linux (Ubuntu Hirsute)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Impish)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Focal)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu Focal)
Status: New => Won't Fix
** Changed in: linux (Ubuntu Hirsute)
Status: New => Confirmed
** Changed in: linux (Ubuntu Impish)
Status: New => Confirmed
** Changed in: linux (Ubuntu Hirsute)
Importance: Undecided => High
** Changed in: linux (Ubuntu Impish)
Importance: Undecided => High
** Also affects: linux-oem-5.10 (Ubuntu)
Importance: Undecided
Status: New
** Changed in: linux-oem-5.10 (Ubuntu Focal)
Status: New => Confirmed
** Changed in: linux-oem-5.10 (Ubuntu Focal)
Importance: Undecided => High
** Changed in: linux-oem-5.10 (Ubuntu Hirsute)
Status: New => Invalid
** Changed in: linux-oem-5.10 (Ubuntu Impish)
Status: New => Invalid
** Also affects: linux-oem-5.13 (Ubuntu)
Importance: Undecided
Status: New
** Changed in: linux-oem-5.13 (Ubuntu Focal)
Importance: Undecided => High
** Changed in: linux-oem-5.13 (Ubuntu Focal)
Status: New => Confirmed
** Changed in: linux-oem-5.13 (Ubuntu Hirsute)
Status: New => Invalid
** Changed in: linux-oem-5.13 (Ubuntu Impish)
Status: New => Invalid
** Tags added: oem-priority originate-from-1933798 stella
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https://bugs.launchpad.net/bugs/1936682
Title:
Fix kernel panic caused by legacy devices on AMD platforms
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