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[47.55.122.23]) by smtp.gmail.com with ESMTPSA id h19-20020a05620a401300b006eeb185c209sm2752971qko.50.2022.10.13.05.43.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Oct 2022 05:43:30 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.95) (envelope-from ) id 1oixYf-002fJN-2g; Thu, 13 Oct 2022 09:43:29 -0300 Date: Thu, 13 Oct 2022 09:43:29 -0300 From: Jason Gunthorpe To: "Radovanovic, Aleksandar" Cc: "Gupta, Nipun" , Marc Zyngier , Robin Murphy , "robh+dt@kernel.org" , "krzysztof.kozlowski+dt@linaro.org" , "gregkh@linuxfoundation.org" , "rafael@kernel.org" , "eric.auger@redhat.com" , "alex.williamson@redhat.com" , "cohuck@redhat.com" , "Gupta, Puneet (DCG-ENG)" , "song.bao.hua@hisilicon.com" , "mchehab+huawei@kernel.org" , "f.fainelli@gmail.com" , "jeffrey.l.hugo@gmail.com" , "saravanak@google.com" , "Michael.Srba@seznam.cz" , "mani@kernel.org" , "yishaih@nvidia.com" , "will@kernel.org" , "joro@8bytes.org" , "masahiroy@kernel.org" , "ndesaulniers@google.com" , "linux-arm-kernel@lists.infradead.org" , "linux-kbuild@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" , "kvm@vger.kernel.org" , "okaya@kernel.org" , "Anand, Harpreet" , "Agarwal, Nikhil" , "Simek, Michal" , "git (AMD-Xilinx)" Subject: Re: [RFC PATCH v3 4/7] bus/cdx: add cdx-MSI domain with gic-its domain as parent Message-ID: References: <20220803122655.100254-1-nipun.gupta@amd.com> <20220906134801.4079497-1-nipun.gupta@amd.com> <20220906134801.4079497-5-nipun.gupta@amd.com> <87h71juxuk.wl-maz@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221013_054335_792423_554A8314 X-CRM114-Status: GOOD ( 24.10 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Oct 12, 2022 at 03:09:26PM +0000, Radovanovic, Aleksandar wrote: > > On Wed, Oct 12, 2022 at 01:37:54PM +0000, Radovanovic, Aleksandar wrote: > > > > On Wed, Oct 12, 2022 at 10:34:23AM +0000, Radovanovic, Aleksandar > > wrote: > > > > > > > > > > > > > As for GITS_TRANSLATER, we can take up to 4 different IOVAs, which > > > > > limits us to 4 CDX devices (should be sufficient for current HW > > > > > use-cases). Also, it means that the address part must be the same > > > > > for all vectors within a single CDX device. I'm assuming this is > > > > > OK as it is going to be a single interrupt and IOMMU domain anyway. > > > > > > > > This is not at all how MSI is supposed to work. > > > > > > In the general case, no, they're not. > > > > I don't mean that you can hack this to work - I mean that in MSI the > > addr/data is supposed to come from the end point itself, not from some kind > > of shared structure. This is important because the actual act of generating > > the write has to be coherent with the DMA the device is doing, as the MSI > > write must push any DMA data to visibility to meet the "producer / > > consumer" model. > > > > I'm not sure I follow your argument, the limitation here is that the MSI > address value is shared between vectors of the same device (requester id > or endpoint, whichever way you prefer to call it), not between > devices. That isn't what you said, you said "we can take up to 4 different IOVAs, which limits us to 4 CDX devices" - which sounds like HW being shared across devices?? Jason _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel