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[47.54.130.67]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8f4724bab9esm57511866d6.42.2026.07.03.09.49.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Jul 2026 09:49:15 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wfh4k-00000008F7B-0pi6; Fri, 03 Jul 2026 13:49:14 -0300 Date: Fri, 3 Jul 2026 13:49:14 -0300 From: Jason Gunthorpe To: Robin Murphy Cc: will@kernel.org, joro@8bytes.org, jpb@kernel.org, catalin.marinas@arm.com, yangyicong@hisilicon.com, linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, stable@vger.kernel.org Subject: Re: [PATCH] iommu/arm-smmu-v3: Add HAFT support for SVA Message-ID: <20260703164914.GY7525@ziepe.ca> References: <878cd6bcbbe2d5677d2f63da13294c148268552c.1782927917.git.robin.murphy@arm.com> Precedence: bulk X-Mailing-List: stable@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: <878cd6bcbbe2d5677d2f63da13294c148268552c.1782927917.git.robin.murphy@arm.com> On Wed, Jul 01, 2026 at 06:45:17PM +0100, Robin Murphy wrote: > @@ -211,6 +213,9 @@ bool arm_smmu_sva_supported(struct arm_smmu_device *smmu) > if (system_supports_bbml2_noabort()) > feat_mask |= ARM_SMMU_FEAT_BBML2; > > + if (system_supports_haft()) > + feat_mask |= ARM_SMMU_FEAT_HAFT; I fear this is going to make SVA stop working on systems it currently does work on, so it might be a major regression. SMMU HTTU is not a commonly implemented feature.. I think of all the NVIDIA ARM chips only one supports it. Given that a quick internal check is raising concerns this will be breaking for us. We need to check in more detail which cores have HAFT. Breaking already deployed SVA would be a major functional regression. I think this should start by just enabling SMMU HAFT when CPU HAFT is on, when possible. Maybe print a warning on the mismatch instead of failing. Since we can't break already deployed SVA a full solution would either have to somehow turn off CPU HAFT or we ignore the gap in the AF updates.. Jason