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Clark" Subject: Re: [PATCH v2 1/2] iommu/amd: Add PerfOpt IOMMU performance optimization support Message-ID: <20260925001718.GC163130@ziepe.ca> References: <20260908041207.38113-1-mario.limonciello@amd.com> <20260908041207.38113-2-mario.limonciello@amd.com> <20260924225018.GB16465@ziepe.ca> <5a6ba6f3-4d8b-4d67-8e5a-ffbe22126464@kernel.org> 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: <5a6ba6f3-4d8b-4d67-8e5a-ffbe22126464@kernel.org> On Thu, Sep 24, 2026 at 07:03:56PM -0500, Mario Limonciello wrote: > > > On 9/24/26 5:50 PM, Jason Gunthorpe wrote: > > On Mon, Sep 07, 2026 at 11:12:06PM -0500, Mario Limonciello wrote: > > > +EXPORT_SYMBOL_GPL(amd_iommu_enable_perfopt); > > > > Last time we hardwired the GPU and IOMMU drivers together it was a > > huge mess to undo. > > > > Why does the GPU driver have to request this? Why can't the iommu > > driver know that this is a special device that can use this magic fast > > path and then auto set it when identity is asked for? > > The reason was to allow an "opt-out" path on the GPU driver. This seems like a very poor reason for doing this given the past negative experiances. Jason