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 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1936682 Title: Fix kernel panic caused by legacy devices on AMD platforms To manage notifications about this bug go to: https://bugs.launchpad.net/hwe-next/+bug/1936682/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs