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
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:
Confirmed
Status in linux-oem-5.13 source package in Focal:
Confirmed
Status in linux source package in Hirsute:
Confirmed
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.
To manage notifications about this bug go to:
https://bugs.launchpad.net/hwe-next/+bug/1936682/+subscriptions
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