From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E23A9C9832F for ; Mon, 28 Sep 2026 08:43:54 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2D83610E860; Mon, 28 Sep 2026 08:43:17 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=fail reason="signature verification failed" (2048-bit key; secure) header.d=infradead.org header.i=@infradead.org header.b="vCL999nq"; dkim-atps=neutral Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3211410E774 for ; Mon, 28 Sep 2026 05:17:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=4ZS6kstd6BIICwqAN1M2ypMQk8KRKCHT0lhVaYKNm1A=; b=vCL999nq/HIPd5KJ+zOLTAyz4G Aw+mGCRquekPCRK6EW4p/d6S76wWDKPuh+mMXENLfmRIi4gbC2DdaKKzsGgZMNfNTZocf5qcOGgrn Qd+BdMZauAbgFut1usVOeVGIswhc+/dd9d3D5o2i2P6lpryuXbcqPzlZYPlmjwD0JwzLQKRZUCLhl 6wMN4QhKY//mhh/rk6iba/taGwIG58PXYCMpH8q1P3BQVR54tPRo5kt/3UlGC2C06rzie1PDXSqy6 jVDOaIJ8iSWGQpWuOUEdLwxdfeo7HId8mIXZovj6TNHeJwP/UXn/OapGxmd6S7g1Hzak2INU72ltH sVSnI2UQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.99.1 #2 (Red Hat Linux)) id 1xB3jc-0000000HLnt-2UJA; Mon, 28 Sep 2026 05:17:04 +0000 Date: Sun, 27 Sep 2026 22:17:04 -0700 From: Christoph Hellwig To: Jason Gunthorpe Cc: Mario Limonciello , Alex Deucher , Joerg Roedel , amd-gfx@lists.freedesktop.org, Suravee Suthikulpanit , Vasant Hegde , Will Deacon , Robin Murphy , "open list:AMD IOMMU (AMD-VI)" , Jatin Kataria , Boqun Feng , "Derek J . Clark" Subject: Re: [PATCH v2 1/2] iommu/amd: Add PerfOpt IOMMU performance optimization support Message-ID: References: <20260908041207.38113-1-mario.limonciello@amd.com> <20260908041207.38113-2-mario.limonciello@amd.com> <20260924225018.GB16465@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260924225018.GB16465@ziepe.ca> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Mailman-Approved-At: Mon, 28 Sep 2026 08:43:05 +0000 X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" On Thu, Sep 24, 2026 at 07:50:18PM -0300, 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. Every time a driver depends on an exact iommu driver is a major design problem. > 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? > > How does the GPU driver even know it is magic special? Yes. And WTF is "perfopt" supposed to mean. Everything is a performance optimization.