Re: [PATCH 0/2] SMMU v3 CMDQ fix and improvement

[Mostafa Saleh <smostafa@google.com>]

On Wed, Sep 24, 2025 at 10:54:36AM -0700, Jacob Pan wrote:
> Hi Will et al,
> 
> These two patches are derived from testing SMMU driver with smaller CMDQ
> sizes where we see soft lockups.
> 
> This happens on HyperV emulated SMMU v3 as well as baremetal ARM servers
> with artificially reduced queue size and microbenchmark to stress test
> concurrency.

Is it possible to share what are the artificial sizes and does the HW/emulation
support range invalidation (IRD3.RIL)?

I'd expect it would be really hard to overwhelm the command queue, unless the
HW doesn't support range invalidation and/or the queue entries are close to
the number of CPUs.

Thanks,
Mostafa


> 
> Thanks,
> 
> Jacob 
> 
> 
> Alexander Grest (1):
>   iommu/arm-smmu-v3: Improve CMDQ lock fairness and efficiency
> 
> Jacob Pan (1):
>   iommu/arm-smmu-v3: Fix CMDQ timeout warning
> 
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 85 +++++++++------------
>  1 file changed, 35 insertions(+), 50 deletions(-)
> 
> -- 
> 2.43.0
>