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[34.126.98.232]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-315f5384107sm17193429a91.5.2025.07.01.15.51.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Jul 2025 15:51:28 -0700 (PDT) Date: Tue, 1 Jul 2025 22:51:20 +0000 From: Pranjal Shrivastava To: Nicolin Chen Cc: jgg@nvidia.com, kevin.tian@intel.com, corbet@lwn.net, will@kernel.org, bagasdotme@gmail.com, robin.murphy@arm.com, joro@8bytes.org, thierry.reding@gmail.com, vdumpa@nvidia.com, jonathanh@nvidia.com, shuah@kernel.org, jsnitsel@redhat.com, nathan@kernel.org, peterz@infradead.org, yi.l.liu@intel.com, mshavit@google.com, zhangzekun11@huawei.com, iommu@lists.linux.dev, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-tegra@vger.kernel.org, linux-kselftest@vger.kernel.org, patches@lists.linux.dev, mochs@nvidia.com, alok.a.tiwari@oracle.com, vasant.hegde@amd.com, dwmw2@infradead.org, baolu.lu@linux.intel.com Subject: Re: [PATCH v7 27/28] iommu/tegra241-cmdqv: Add user-space use support Message-ID: References: <539ee2ec112162abdba511574e2205a77b425059.1750966133.git.nicolinc@nvidia.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Jul 01, 2025 at 03:07:57PM -0700, Nicolin Chen wrote: > 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) > Right exactly what got me confused. I was assuming the same CMDQV driver would run in the Guest kernel but seems like there's another driver for the Guest that's not in tree yet or maybe is a purely user-space thing? And the weird part was that "invalidation" commands are accelerated but we use the .cache_invalidate viommu op for `non-invalidation` commands. But I guess what you meant there could be non-accelerated invalidation commands (maybe something stage 2 TLBIs?) which would go through the .cache_invalidate op, right? > Nicolin Praan