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[142.167.219.86]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c5b92ec55esm142292885a.55.2025.03.21.08.30.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Mar 2025 08:30:35 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1tveKR-000000014u5-005h; Fri, 21 Mar 2025 12:30:35 -0300 Date: Fri, 21 Mar 2025 12:30:34 -0300 From: Jason Gunthorpe To: Pranjal Shrivastava Cc: Mostafa Saleh , Robin Murphy , Joerg Roedel , Will Deacon , Nicolin Chen , Daniel Mentz , iommu@lists.linux.dev Subject: Re: [RFC PATCH 0/5] iommu/arm-smmu-v3: Implement Runtime/System Sleep ops Message-ID: <20250321153034.GN126678@ziepe.ca> References: <20250319004254.2547950-1-praan@google.com> <5b29ea3b-ba8a-4f7a-b241-4ed5b1985a1f@arm.com> <20250319194609.GA126678@ziepe.ca> <20250320230551.GL126678@ziepe.ca> 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 Fri, Mar 21, 2025 at 02:44:09PM +0000, Pranjal Shrivastava wrote: > However, still there's a worry about the reset value of GBPA.Abort as > pointed out by Robin earlier. Since the reset value of GBPA.Abort is > implementation defined.. there's a chance that after a power cycle the > SMMU wakes up with GBPA configured to bypass.. in such a case, I don't > think the kernel should be responsible to ensure security.. The kernel should be responsible to operate that HW in a secure way. If the spec doesn't guarentee security then you will need a ACPI/DT flag to indicate if specific implementations are secure or not (ie if the implementation preserves GBPA.Abort). Otherwise we'd have to architect around the insecurity somehow and prevent the SMMU from unpowering if there is any security sensitive attachment.. Jason