linux-kernel - Re: [PATCH v7 27/28] iommu/tegra241-cmdqv: Add user-space use support

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Message-ID: <aGRcPSwaJkTeUrMx@Asurada-Nvidia>
Date: Tue, 1 Jul 2025 15:07:57 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: Pranjal Shrivastava <praan@...gle.com>
CC: <jgg@...dia.com>, <kevin.tian@...el.com>, <corbet@....net>,
	<will@...nel.org>, <bagasdotme@...il.com>, <robin.murphy@....com>,
	<joro@...tes.org>, <thierry.reding@...il.com>, <vdumpa@...dia.com>,
	<jonathanh@...dia.com>, <shuah@...nel.org>, <jsnitsel@...hat.com>,
	<nathan@...nel.org>, <peterz@...radead.org>, <yi.l.liu@...el.com>,
	<mshavit@...gle.com>, <zhangzekun11@...wei.com>, <iommu@...ts.linux.dev>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-tegra@...r.kernel.org>,
	<linux-kselftest@...r.kernel.org>, <patches@...ts.linux.dev>,
	<mochs@...dia.com>, <alok.a.tiwari@...cle.com>, <vasant.hegde@....com>,
	<dwmw2@...radead.org>, <baolu.lu@...ux.intel.com>
Subject: Re: [PATCH v7 27/28] iommu/tegra241-cmdqv: Add user-space use support

On Tue, Jul 01, 2025 at 08:43:30PM +0000, Pranjal Shrivastava wrote:
> On Tue, Jul 01, 2025 at 01:23:17PM -0700, Nicolin Chen wrote:
> > Or perhaps calling them "non-accelerated commands" would be nicer.
> 
> Uhh okay, so there'll be a separate driver in the VM issuing invalidation
> commands directly to the CMDQV thus we don't see any of it's part here?

That's how it works. VM must run a guest-level VCMDQ driver that
separates accelerated and non-accelerated commands as it already
does:

    accelerated commands => VCMDQ (HW)
non-accelerated commands => SMMU CMDQ (SW) =iommufd=> SMMU CMDQ (HW)

Nicolin