[Bug 2145771] Re: Firmware bug on Snapdragon laptops causes crashes on Laptops with > 32GB RAM

[Launchpad Bug Tracker]

This bug was fixed in the package ubuntu-x1e-settings - 33

---------------
ubuntu-x1e-settings (33) resolute; urgency=medium

  * Add GRUB_BADRAM to mitigate firmware crashes on machines with
    more than 32 GB RAM (LP: #2145771)

 -- Tobias Heider <tobias.heider at canonical.com>  Mon, 23 Mar 2026
23:41:13 +0100

** Changed in: ubuntu-x1e-settings (Ubuntu)
       Status: New => Fix Released

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https://bugs.launchpad.net/bugs/2145771

Title:
  Firmware bug on Snapdragon laptops causes crashes on Laptops with >
  32GB RAM

Status in ubuntu-x1e-settings package in Ubuntu:
  Fix Released

Bug description:
  The bug is best described in the second half of the following mail:
  https://lore.kernel.org/all/aSl48gV9laFb-MR1@linaro.org/

  > # EL1 with Gunyah hypervisor
  >
  > For EL1, the hypervisor firmware used on most retail laptops limits the
  > usable DMA memory in the SMMUs to the physical 36-bit range. You are
  > right that laptops with 64 GiB memory are essentially unusable in EL1
  > without disabling the physical memory outside the 36-bit range, but
  > applying this patch would make it even worse.
  > 
  > There are two separate cases:
  >
  > - For devices behind the SMMUv2, the situation should be the same as
  >   above. Increased IOVA space, but no effect on physical address range.
  >   This is what is currently causing crashes with 64 GiB RAM in EL1.
  >
  > - Devices behind the SMMUv3 (PCIe) do not have an IOMMU assigned when
  >   running in EL1. In this case, the 36-bit dma-ranges prevents PCIe
  >   devices from using memory outside the 36-bit range. They will fall
  >   back to bounce buffers in that case. Applying your patch will disable
  >   that, making it even more likely to crash than before.

  We already ship a workaround in our livecd grub config where we add "cutmem 0x8800000000 0x8fffffffff".
  I didn't initially add it for the installed system too because my machine works mostly fine without.
  We now have multiple user reports that nothing works at all unless memory usage
  is restricted, see:
  https://oftc.catirclogs.org/aarch64-laptops/2026-03-23#35173487;
  https://oftc.catirclogs.org/aarch64-laptops/2026-03-23#35173540;

  At this point I think we should ship a /etc/default/grub.d/ config that limits
  the memory for everyone by default, people who don't need it can still opt-in
  by modifying the config themselves.

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