KVM guest crashes with a "Bad address" error when accessing GPU memory (specifically drm_gem_shmem pfn_mkwrite) on kernel 7.1.5-400.asahi

[art0tod]

asahi-diagnose-20260802-200702.txt

System Details

• Hardware: MacBook Pro 14" (2021, Apple M1 Pro)
• OS: Fedora Asahi Remix 44 (aarch64, 16K pages)
• Kernel: 7.1.5-400.asahi.fc44.aarch64+16k
• Packages: muvm 0.6.0-3.fc44, fex-emu 2604-1.fc44, steam 0-14.fc44

Any KVM guest attempting to access host GPU memory crashes the entire VM with the error:
[ERROR krun_vmm::linux::vstate] Failure during vcpu run: Bad address (os error 14)

The crash occurs when running Steam on Asahi inside muvm using the default GPU mode. The VM dies immediately upon Steam client GL initialization. Switching to muvm --gpu-mode=software resolves the issue, isolating the fault to GPU memory access.

Guest Log Snippet

steam.sh[244]: Running Steam on fedora-asahi-remix 44 64-bit
steam.sh[244]: STEAM_RUNTIME is enabled automatically
setup.sh[329]: Updating Steam runtime environment...
[ERROR krun_vmm::linux::vstate] Failure during vcpu run: Bad address (os error 14)

Reproduction Steps

1. Install on Fedora Asahi Remix 44 (M1/M2, 16K kernel): sudo dnf install steam
2. Run Steam:
   muvm -- FEXBash -c "/home/user/.local/share/fex-steam/steam-launcher/bin_steam.sh -cef-force-occlusion"
3. Observation: The guest crashes with Failure during vcpu run: Bad address (os error 14) at GL init.
4. Running the same command with --gpu-mode=software works fine.