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Fri, 24 Jul 2026 08:25:41 -0700 (PDT) Received: from jgg by NV-9X0Z6D3.localdomain with local (Exim 4.97) (envelope-from ) id 1wnHmO-000000002o5-3k7t; Fri, 24 Jul 2026 12:25:40 -0300 Date: Fri, 24 Jul 2026 12:25:40 -0300 From: Jason Gunthorpe To: Will Deacon Cc: Robin Murphy , nicolinc@nvidia.com, 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: 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: On Wed, Jul 22, 2026 at 11:20:48PM +0100, Will Deacon wrote: > > We might block traffic in the process of _explicitly blocking traffic_!? > > Whoop-de-do, surely? > > Hmm. I have very vague memories that there were some virtualisation (?) > cases where Jason and Nicolin cared about the type of event that would > be generated by concurrent DMA (e.g. bad CD vs translation fault) but > maybe I'm misremembering. Yeah, it is actually important for that special SVA mm drop/release case. We need to write a CD that blocks walking but always generates translation fault. I'm away from my computer right now, but if sashiko is saying that the SVA flow that uses EPD generates a racy bad CD then that is a bug that needs to be fixed. Possibly by ignoring HAFT in the used calculation for the EPD cases. We should also try to have a kunit to cover that specific mm drop flow in the SVA code. Jason