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[47.54.130.67]) by smtp.gmail.com with ESMTPSA id af79cd13be357-907b918cffesm1444739385a.14.2026.05.12.08.11.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 May 2026 08:11:34 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wMolh-00000000ATo-2WZI; Tue, 12 May 2026 12:11:33 -0300 Date: Tue, 12 May 2026 12:11:33 -0300 From: Jason Gunthorpe To: Joonwon Kang Cc: robin.murphy@arm.com, Alexander.Grest@microsoft.com, amhetre@nvidia.com, baolu.lu@linux.intel.com, easwar.hariharan@linux.microsoft.com, iommu@lists.linux.dev, jacob.jun.pan@linux.intel.com, joro@8bytes.org, jpb@kernel.org, kees@kernel.org, kevin.tian@intel.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, nicolinc@nvidia.com, praan@google.com, smostafa@google.com, will@kernel.org Subject: Re: [PATCH RFC] iommu: Enable per-device SSID space for SVA Message-ID: <20260512151133.GD7702@ziepe.ca> References: <20260512145138.3414002-1-joonwonkang@google.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20260512145138.3414002-1-joonwonkang@google.com> On Tue, May 12, 2026 at 02:51:38PM +0000, Joonwon Kang wrote: > Appreciate all your clarifications here. So, my understanding is that if > our system does not support ST64BV and ST64BV0 or if our device does not > distinguish between the posted write and the non-posted write regarding > PASID, then we can lift the use of the global PASID space. Can I say this? You should do what Robin said - just have your driver use a per-device PASID that it allocates and never use the global pasid allocator. To do this lightly re-organize the SVA code so the driver can supply its own PASID, and in this mode we wouldn't activate the ENQCMD features in the mm. Jason