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Thu, 14 Aug 2025 17:40:01 -0700 (PDT) Received: from ziepe.ca ([130.41.10.202]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-310ab87a099sm3458fac.1.2025.08.14.17.39.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Aug 2025 17:40:00 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1umiUA-00000003TLB-28WR; Thu, 14 Aug 2025 21:39:58 -0300 Date: Thu, 14 Aug 2025 21:39:58 -0300 From: Jason Gunthorpe To: Shyam Saini Cc: iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, virtualization@lists.linux.dev, will@kernel.org, jacob.pan@linux.microsoft.com, eric.auger@redhat.com, code@tyhicks.com, eahariha@linux.microsoft.com, vijayb@linux.microsoft.com, bboscaccy@linux.microsoft.com, robh@kernel.org, saravanak@google.com, krzk+dt@kernel.org, conor+dt@kernel.org, lizhi.hou@amd.com, clement.leger@bootlin.com Subject: Re: [PATCH v3 2/3] iommu/of: fix device tree configuration for PCI devices Message-ID: <20250815003958.GE599331@ziepe.ca> References: <20250806215539.1240561-1-shyamsaini@linux.microsoft.com> <20250806215539.1240561-3-shyamsaini@linux.microsoft.com> <20250808121515.GE377696@ziepe.ca> <20250814233018.GA31418@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250814233018.GA31418@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> On Thu, Aug 14, 2025 at 04:30:18PM -0700, Shyam Saini wrote: > or were you referring to [2]? > > In that case, the PCI child node data needs to be parsed, which is > currently handled individually by each host controller driver. Yes, this looks like it may be what I was thinking of, the pci@1,0 specifes the BDF effectively > This might not be a strong argument, but since firmware updates tend > to happen less frequently than OS updates, any addition or modification > to the FDT would require a firmware update. Wouldn't it be more > maintainable to keep this logic in Linux, which is easier to update > and typically updated more often? The DT is supposed to describe the HW, if the PCI device has an issue with its dma ranges then it seems reasonable to me the FW will use the existing standards based way to describe that issue? Presumably this is a fixed issue of the platform. You never did explain how your system has such werdio behavior, or how something like iommu=pt can function on it... Jason