linux-kernel - Re: [PATCH v2 1/2] iommu/arm-smmu-v3: Fix CMDQ timeout warning

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Message-ID: <20251104113728.0000568e@linux.microsoft.com>
Date: Tue, 4 Nov 2025 11:37:28 -0800
From: Jacob Pan <jacob.pan@...ux.microsoft.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: <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>, Zhang Yu
 <zhangyu1@...ux.microsoft.com>, Jean Philippe-Brucker
 <jean-philippe@...aro.org>, Alexander Grest <Alexander.Grest@...rosoft.com>
Subject: Re: [PATCH v2 1/2] iommu/arm-smmu-v3: Fix CMDQ timeout warning

Hi Nicolin,

On Tue, 4 Nov 2025 10:48:31 -0800
Nicolin Chen <nicolinc@...dia.com> wrote:

> On Tue, Nov 04, 2025 at 10:25:39AM -0800, Jacob Pan wrote:
> > > -----------------------------------------------------------------
> > > 
> > > And the commit message should point out:
> > > 
> > > The existing arm_smmu_cmdq_poll_until_not_full() doesn't fit
> > > efficiently nor ideally to the only caller
> > > arm_smmu_cmdq_issue_cmdlist():
> > >  - It uses a new timer at every single call, which fails to limit
> > > to the preset ARM_SMMU_POLL_TIMEOUT_US per issue.  
> 
> > Not following what you mean.
> > The original code below does honor the timeout of
> > ARM_SMMU_POLL_TIMEOUT_US  
> 
> It sets the timeout per arm_smmu_cmdq_poll_until_not_full(), not
> the entire wait-for-space routine. And that's why you moved the
> queue_poll_init() to the caller, right?
> 
Got you! will do.

Thanks,

Jacob