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Received: from MN2PR12MB3613.namprd12.prod.outlook.com (2603:10b6:208:c1::17) by SN7PR12MB6791.namprd12.prod.outlook.com (2603:10b6:806:268::22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9253.13; Mon, 27 Oct 2025 23:26:41 +0000 Received: from MN2PR12MB3613.namprd12.prod.outlook.com ([fe80::1b3b:64f5:9211:608b]) by MN2PR12MB3613.namprd12.prod.outlook.com ([fe80::1b3b:64f5:9211:608b%4]) with mapi id 15.20.9253.017; Mon, 27 Oct 2025 23:26:41 +0000 Date: Mon, 27 Oct 2025 20:26:40 -0300 From: Jason Gunthorpe To: Nicolin Chen Cc: joro@8bytes.org, kevin.tian@intel.com, suravee.suthikulpanit@amd.com, will@kernel.org, robin.murphy@arm.com, sven@kernel.org, j@jannau.net, jean-philippe@linaro.org, robin.clark@oss.qualcomm.com, dwmw2@infradead.org, baolu.lu@linux.intel.com, yong.wu@mediatek.com, matthias.bgg@gmail.com, angelogioacchino.delregno@collabora.com, tjeznach@rivosinc.com, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, heiko@sntech.de, schnelle@linux.ibm.com, mjrosato@linux.ibm.com, wens@csie.org, jernej.skrabec@gmail.com, samuel@sholland.org, thierry.reding@gmail.com, jonathanh@nvidia.com, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, asahi@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-riscv@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-s390@vger.kernel.org, linux-sunxi@lists.linux.dev, linux-tegra@vger.kernel.org, virtualization@lists.linux.dev, patches@lists.linux.dev Subject: Re: [PATCH v1 03/20] iommu/arm-smmu-v3: Implement arm_smmu_domain_test_dev Message-ID: <20251027232640.GE1018328@nvidia.com> References: <20251020163231.GX316284@nvidia.com> Content-Type: text/plain; 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It can't simply go through a regular attach_dev call since > driver wouldn't expect any inconsistency in the core. > > Driver would have to be aware of the reset state, and make a copy > of the old domain's CD/STE to use for a test_dev() during a reset. It seems convoluted :\ IDK if you want to do that some kind of "attach but really don't" flag so all the tracking was kept, just the STE was forced to blocking. Then since all the fake attaches are tracked and validated switching to a real ste shouldn't fail. For instance SMMU could continue to build the CD table and act like the CD is active, but the STE wouldn't point to it. Basically, this approach doesn't seem to solve all the problems, it reduces them sure, but there are still enough gaps. So I think we either have to live with them and call it a user bug to change the domain improperly during FLR.. If it happens dump the translation into blocking and move on.. Or we have to do some kind of fake attach tracking which doesn't sound appealing.. Jason