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[159.2.239.150]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-90e9eef4f20sm7284946d6.41.2026.09.01.18.51.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Sep 2026 18:51:38 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1x1a8X-0000000Czw5-2tb4; Tue, 01 Sep 2026 22:51:37 -0300 Date: Tue, 1 Sep 2026 22:51:37 -0300 From: Jason Gunthorpe To: Nicolin Chen Cc: "Aneesh Kumar K.V" , linux-coco@lists.linux.dev, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Alexey Kardashevskiy , Catalin Marinas , Dan Williams , Joerg Roedel , Jonathan Cameron , Marc Zyngier , Pranjal Shrivastava , Robin Murphy , Samuel Ortiz , Steven Price , Suzuki K Poulose , Will Deacon , Xu Yilun Subject: Re: [RFC PATCH v4 03/16] iommu/arm-smmu-v3: Add initial pSMMU realm viommu plumbing Message-ID: <20260902015137.GA2890729@ziepe.ca> References: <20260427085344.941627-1-aneesh.kumar@kernel.org> <20260427085344.941627-4-aneesh.kumar@kernel.org> <20260901143445.GC56830@ziepe.ca> <20260901174230.GA2847102@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260901_185141_173121_C631E7F5 X-CRM114-Status: GOOD ( 13.94 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Sep 01, 2026 at 12:08:38PM -0700, Nicolin Chen wrote: > The viommu object here is an empty vehicle that almost has no use > but to allow another vehicle (vdevice) on top to forward vBDF. It > makes VMM code a bit awkward: there is no iommu instance, so VMM > doesn't enable iommu driver, then there is no good place to alloc > the viomu object for VIOMMU_TYPE_ARM_REALM_SMMUV3. It would have to allocate singletons viommu for each psmmu as part of setting up the vdevices. Somehow I'd rather the vmm deal with that then invent a whole new set of uapis and flows.. At best maybe we can invent a kernel side helper to create the singletons like the auto domains, but IDK if it is really so hard for the VMM (especially compared with how hard everything else is in CC) Jason