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 X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1ED45C433E0 for ; Fri, 5 Jun 2020 23:19:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E748B207DF for ; Fri, 5 Jun 2020 23:19:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591399154; bh=pxsClvnIPBaS8ODkk62CMx4DJx6gcP1jIo9ANMgure4=; h=Date:From:To:Cc:Subject:In-Reply-To:List-ID:From; b=G9CM7jcxSFc/FtQPw2UClnIbsID+W5A3bJ82Di4JhAwFPRgIDVuJ1UFahjMVZGO1v DDQpaxLLemcD7/dSzRNKKYZTpFzNSXF0sihQ6i0ESQbjOXGCIv2MNaLHEdYSCoJfWz XV7NPggW18Oo9EH/ezn78KqVydBBJ+fF5alXxT44= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728316AbgFEXTN (ORCPT ); Fri, 5 Jun 2020 19:19:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:47740 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728290AbgFEXTN (ORCPT ); Fri, 5 Jun 2020 19:19:13 -0400 Received: from localhost (mobile-166-175-190-200.mycingular.net [166.175.190.200]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B1CC7207D0; Fri, 5 Jun 2020 23:19:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591399152; bh=pxsClvnIPBaS8ODkk62CMx4DJx6gcP1jIo9ANMgure4=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=cWVCuuhZEXopJ/fy8/HaCu7gj+qdiUHK7yyWdnF7I+g00606Q27D/lHhs2F+KUUbI qPalWOJ7gwNYAzD0Zb2lhQotEE4HBkdYrzhA669gi2oRrAkyKg2JRbaRxC86n+xjd9 CZzarVVqj34lwCRUNnhR0Wkc6VA4FmF+zD+p5VbA= Date: Fri, 5 Jun 2020 18:19:09 -0500 From: Bjorn Helgaas To: Zhangfei Gao Cc: Joerg Roedel , Bjorn Helgaas , Arnd Bergmann , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , "Rafael J. Wysocki" , Len Brown , jean-philippe , Greg Kroah-Hartman , Herbert Xu , kenneth-lee-2012@foxmail.com, Wangzhou , linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, iommu@lists.linux-foundation.org, linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org Subject: Re: [PATCH 0/2] Introduce PCI_FIXUP_IOMMU Message-ID: <20200605231909.GA1155454@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <779f4044-cf6a-b0d3-916f-0274450c07d3@linaro.org> Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Thu, Jun 04, 2020 at 09:33:07PM +0800, Zhangfei Gao wrote: > On 2020/6/2 上午1:41, Bjorn Helgaas wrote: > > On Thu, May 28, 2020 at 09:33:44AM +0200, Joerg Roedel wrote: > > > On Wed, May 27, 2020 at 01:18:42PM -0500, Bjorn Helgaas wrote: > > > > Is this slowdown significant? We already iterate over every device > > > > when applying PCI_FIXUP_FINAL quirks, so if we used the existing > > > > PCI_FIXUP_FINAL, we wouldn't be adding a new loop. We would only be > > > > adding two more iterations to the loop in pci_do_fixups() that tries > > > > to match quirks against the current device. I doubt that would be a > > > > measurable slowdown. > > > I don't know how significant it is, but I remember people complaining > > > about adding new PCI quirks because it takes too long for them to run > > > them all. That was in the discussion about the quirk disabling ATS on > > > AMD Stoney systems. > > > > > > So it probably depends on how many PCI devices are in the system whether > > > it causes any measureable slowdown. > > I found this [1] from Paul Menzel, which was a slowdown caused by > > quirk_usb_early_handoff(). I think the real problem is individual > > quirks that take a long time. > > > > The PCI_FIXUP_IOMMU things we're talking about should be fast, and of > > course, they're only run for matching devices anyway. So I'd rather > > keep them as PCI_FIXUP_FINAL than add a whole new phase. > > > Thanks Bjorn for taking time for this. > If so, it would be much simpler. > > +++ b/drivers/iommu/iommu.c > @@ -2418,6 +2418,10 @@ int iommu_fwspec_init(struct device *dev, struct > fwnode_handle *iommu_fwnode, >         fwspec->iommu_fwnode = iommu_fwnode; >         fwspec->ops = ops; >         dev_iommu_fwspec_set(dev, fwspec); > + > +       if (dev_is_pci(dev)) > +               pci_fixup_device(pci_fixup_final, to_pci_dev(dev)); > + > > Then pci_fixup_final will be called twice, the first in pci_bus_add_device. > Here in iommu_fwspec_init is the second time, specifically for iommu_fwspec. > Will send this when 5.8-rc1 is open. Wait, this whole fixup approach seems wrong to me. No matter how you do the fixup, it's still a fixup, which means it requires ongoing maintenance. Surely we don't want to have to add the Vendor/Device ID for every new AMBA device that comes along, do we? Bjorn