linux-kernel - Re: [PATCH v2 0/2] SMMU v3 CMDQ fix and improvement

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Message-ID: <20251030084238.00003fbf@linux.microsoft.com>
Date: Thu, 30 Oct 2025 08:42:38 -0700
From: Jacob Pan <jacob.pan@...ux.microsoft.com>
To: linux-kernel@...r.kernel.org, "iommu@...ts.linux.dev"
 <iommu@...ts.linux.dev>, Will Deacon <will@...nel.org>, Joerg Roedel
 <joro@...tes.org>, Mostafa Saleh <smostafa@...gle.com>, Jason Gunthorpe
 <jgg@...dia.com>, Robin Murphy <robin.murphy@....com>, Nicolin Chen
 <nicolinc@...dia.com>
Cc: Zhang Yu <zhangyu1@...ux.microsoft.com>, Jean Philippe-Brucker
 <jean-philippe@...aro.org>, Alexander Grest <Alexander.Grest@...rosoft.com>
Subject: Re: [PATCH v2 0/2] SMMU v3 CMDQ fix and improvement

Hi Will,

Just a gentle reminder, appreciated.

@Nicolin, were you able to evaluate these?

By the way, I incorporated your review comments in v2, except for
extracting the function arm_smmu_cmdq_poll_until_enough_space(),
primarily due to concerns with the IRQ flags.

Thanks,

Jacob

 On Mon, 20 Oct 2025 15:43:51 -0700 Jacob
Pan <jacob.pan@...ux.microsoft.com> 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.
> 
> 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 | 97
> ++++++++++----------- 1 file changed, 47 insertions(+), 50
> deletions(-)
>