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[34.76.240.140]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-426ce583664sm40279039f8f.22.2025.10.17.03.57.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Oct 2025 03:57:56 -0700 (PDT) Date: Fri, 17 Oct 2025 10:57:52 +0000 From: Mostafa Saleh To: Jacob Pan Cc: linux-kernel@vger.kernel.org, "iommu@lists.linux.dev" , Will Deacon , Jason Gunthorpe , Robin Murphy , Nicolin Chen , Zhang Yu , Jean Philippe-Brucker , Alexander Grest Subject: Re: [PATCH 0/2] SMMU v3 CMDQ fix and improvement Message-ID: References: <20250924175438.7450-1-jacob.pan@linux.microsoft.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250924175438.7450-1-jacob.pan@linux.microsoft.com> On Wed, Sep 24, 2025 at 10:54:36AM -0700, Jacob Pan wrote: > Hi Will et al, > > These two patches are derived from testing SMMU driver with smaller CMDQ > sizes where we see soft lockups. > > This happens on HyperV emulated SMMU v3 as well as baremetal ARM servers > with artificially reduced queue size and microbenchmark to stress test > concurrency. Is it possible to share what are the artificial sizes and does the HW/emulation support range invalidation (IRD3.RIL)? I'd expect it would be really hard to overwhelm the command queue, unless the HW doesn't support range invalidation and/or the queue entries are close to the number of CPUs. Thanks, Mostafa > > Thanks, > > Jacob > > > Alexander Grest (1): > iommu/arm-smmu-v3: Improve CMDQ lock fairness and efficiency > > Jacob Pan (1): > iommu/arm-smmu-v3: Fix CMDQ timeout warning > > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 85 +++++++++------------ > 1 file changed, 35 insertions(+), 50 deletions(-) > > -- > 2.43.0 >