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

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Message-ID: <aQpKf2IPD5xeBu1K@Asurada-Nvidia>
Date: Tue, 4 Nov 2025 10:48:31 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: Jacob Pan <jacob.pan@...ux.microsoft.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

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?

Nicolin