On Wed, 18 Dec 2024 21:14:21 -0800, Nicolin Chen wrote:
The hardware limitation "max=19" actually comes from SMMU Command Queue. So, it'd be more natural for tegra241-cmdqv driver to read it out rather than hardcoding it itself.
This is not an issue yet for a kernel on a baremetal system, but a guest kernel setting the queue base/size in form of IPA/gPA might result in a noncontiguous queue in the physical address space, if underlying physical pages backing up the guest RAM aren't contiguous entirely: e.g. 2MB-page backed guest RAM cannot guarantee a contiguous queue if it is 8MB (capped to VCMDQ_LOG2SIZE_MAX=19). This might lead to command errors when HW does linear-read from a noncontiguous queue memory.
[...]
Applied to will (for-joerg/arm-smmu/updates), thanks!
[1/1] iommu/tegra241-cmdqv: Read SMMU IDR1.CMDQS instead of hardcoding https://git.kernel.org/will/c/e94dc6ddda8d
Cheers,