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[142.162.112.119]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8cbbf677448sm464268985a.19.2026.02.27.06.01.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Feb 2026 06:01:59 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1vvyPl-00000000vPr-2NW2; Fri, 27 Feb 2026 10:01:57 -0400 Date: Fri, 27 Feb 2026 10:01:57 -0400 From: Jason Gunthorpe To: Antheas Kapenekakis Cc: Robin Murphy , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, Joerg Roedel , Will Deacon , Vasant Hegde , Alejandro Jimenez , dnaim@cachyos.org, Mario.Limonciello@amd.com Subject: Re: [PATCH v1] iommu: Skip mapping at address 0x0 if it already exists Message-ID: <20260227140157.GH44359@ziepe.ca> References: <6bac3817-9652-4146-ab44-2a9518c3b339@arm.com> <7e3a1d3c-64cb-43a8-bd2f-05b24a8d1611@arm.com> <20260227010317.GD44359@ziepe.ca> 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: On Fri, Feb 27, 2026 at 09:06:27AM +0100, Antheas Kapenekakis wrote: > On Fri, 27 Feb 2026 at 02:03, Jason Gunthorpe wrote: > > > > On Thu, Feb 26, 2026 at 09:40:10PM +0100, Antheas Kapenekakis wrote: > > > I am still concerned about unaligned checks. It is a functional change > > > that can cause regressions in all devices. The approach of this patch > > > does not affect behavior in other devices. I would like for Jason to > > > weigh in. > > > > I think Robin's solution is very clever, but I share the concern > > regarding what all the implementations do. > > I will send a V3 with a ternary instead. This way, only 0 is affected. > I will compile test now and test later today. I am impartial with either fix. > > ``` > phys_addr = iommu_iova_to_phys(domain, addr ? addr : 1); > ``` Yeah, that's a good idea Jason