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[34.124.234.44]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2bf218a2535sm343525ad.29.2026.05.28.14.57.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 May 2026 14:57:59 -0700 (PDT) Date: Thu, 28 May 2026 21:57:53 +0000 From: Pranjal Shrivastava To: Nicolin Chen Cc: iommu@lists.linux.dev, Will Deacon , Joerg Roedel , Robin Murphy , Jason Gunthorpe , Mostafa Saleh , Daniel Mentz , Ashish Mhetre , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v7 07/11] iommu/arm-smmu-v3: Add CMDQ_PROD_STOP_FLAG to gate CMDQ submissions Message-ID: References: <20260527221407.1756491-1-praan@google.com> <20260527221407.1756491-8-praan@google.com> 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 Thu, May 28, 2026 at 12:41:35PM -0700, Nicolin Chen wrote: > On Wed, May 27, 2026 at 10:14:03PM +0000, Pranjal Shrivastava wrote: > > Introduce a new bit flag, CMDQ_PROD_STOP_FLAG (bit 30), in the command > > queue's producer index to safely gate command submissions during device > > suspension. > > > > The flag embeds the suspend state directly into the existing global state > > The flag checked in the compxchg loop in arm_smmu_cmdq_issue_cmdlist(), > > s/compxchg/cmpxchg Ack. I'll fix it. > > > which acts as a Point of Commitment, ensuring that no indices are > > reserved or committed once the SMMU begins suspending. > > > > This prevents a situation of "abandoned batches" where indices are > > incremented but commands are never written, which would otherwise > > lead to timeout during the drain poll. > > > > Update queue_inc_prod_n() to preserve this flag during index > > calculations, ensuring that any in-flight commands that successfully > > passed the point of commitment can proceed to completion while the > > flag remains set. > > > > Suggested-by: Daniel Mentz > > Signed-off-by: Pranjal Shrivastava > > Reviewed-by: Nicolin Chen Thanks! Praan