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[35.187.245.222]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-819c530133csm23442851b3a.31.2026.01.14.07.49.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Jan 2026 07:49:26 -0800 (PST) Date: Wed, 14 Jan 2026 15:49:21 +0000 From: Pranjal Shrivastava To: Nicolin Chen Cc: will@kernel.org, jgg@nvidia.com, robin.murphy@arm.com, joro@8bytes.org, linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, skolothumtho@nvidia.com, xueshuai@linux.alibaba.com, smostafa@google.com Subject: Re: [PATCH rc v6 1/4] iommu/arm-smmu-v3: Add update_safe bits to fix STE update sequence Message-ID: References: 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: On Mon, Jan 12, 2026 at 12:20:14PM -0800, Nicolin Chen wrote: > From: Jason Gunthorpe > > C_BAD_STE was observed when updating nested STE from an S1-bypass mode to > an S1DSS-bypass mode. As both modes enabled S2, the used bit is slightly > different than the normal S1-bypass and S1DSS-bypass modes. As a result, > fields like MEV and EATS in S2's used list marked the word1 as a critical > word that requested a STE.V=0. This breaks a hitless update. > > However, both MEV and EATS aren't critical in terms of STE update. One > controls the merge of the events and the other controls the ATS that is > managed by the driver at the same time via pci_enable_ats(). > > Add an arm_smmu_get_ste_update_safe() to allow STE update algorithm to > relax those fields, avoiding the STE update breakages. > > After this change, entry_set has no caller checking its return value, so > change it to void. > > Note that this change is required by both MEV and EATS fields, which were > introduced in different kernel versions. So add get_update_safe() first. > MEV and EATS will be added to arm_smmu_get_ste_update_safe() separately. > > Fixes: 1e8be08d1c91 ("iommu/arm-smmu-v3: Support IOMMU_DOMAIN_NESTED") > Cc: stable@vger.kernel.org > Signed-off-by: Jason Gunthorpe > Reviewed-by: Shuai Xue > Reviewed-by: Mostafa Saleh > Signed-off-by: Nicolin Chen Reviewed-by: Pranjal Shrivastava Thanks!