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[142.167.219.86]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c7a8a0edc8sm1052651985a.110.2025.04.16.05.02.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Apr 2025 05:02:51 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1u51Tf-00000004JDK-0sd4; Wed, 16 Apr 2025 09:02:51 -0300 Date: Wed, 16 Apr 2025 09:02:51 -0300 From: Jason Gunthorpe To: Pranjal Shrivastava Cc: Nicolin Chen , Joerg Roedel , Will Deacon , Robin Murphy , Mostafa Saleh , Daniel Mentz , iommu@lists.linux.dev Subject: Re: [RFC PATCH 3/5] iommu/arm-smmu-v3: Implement pm_runtime & system sleep ops Message-ID: <20250416120251.GC493866@ziepe.ca> References: <20250319004254.2547950-1-praan@google.com> <20250319004254.2547950-4-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 Wed, Apr 16, 2025 at 10:24:52AM +0000, Pranjal Shrivastava wrote: > Also, this would mean that we'll have to take care if the Guest Kernel > ends up touching the mmio region while the SMMU is suspended? I think this is approaching it backwards. If power management is supported then the power should be on unless the VM has activated its own virtual power management. VM virtual power mangement would flush the cmdq from the VM side then signal the host that it is OK to power down the SMMU, which the host may or may not do It doesn't make alot of sense to power down the SMMU while a VM is running... Jason