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 6A2D7C433E1 for ; Mon, 8 Jun 2020 16:41:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4684820774 for ; Mon, 8 Jun 2020 16:41:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591634517; bh=9+wSpwKeMW/wdGvPemQJqQQABIsLkQPW2K8a1nmcHm0=; h=Date:From:To:Cc:Subject:In-Reply-To:List-ID:From; b=uz+mpO/DSYrFQsHk+GDRFlNRuurzbp6rJRNpgBnG9IrGl4LsQheNCVfi6lOmUyGwk eFQ8o1yocT23K9A8tC6aIX9XYWxMsjSDozF6jKQkulYnuWJ/PKzFWtMnNdS35s7el0 CbRXtXTvlA5wy5LJrJ4g9vvGzzZ4rlPMIJIE0mQc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387422AbgFHQl4 (ORCPT ); Mon, 8 Jun 2020 12:41:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:46908 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730571AbgFHQl4 (ORCPT ); Mon, 8 Jun 2020 12:41:56 -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 94E0D206A4; Mon, 8 Jun 2020 16:41:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591634515; bh=9+wSpwKeMW/wdGvPemQJqQQABIsLkQPW2K8a1nmcHm0=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=vcbz31UJVkE9u265rOeW3ymi3j4Td/cEnamY/yY9ERI7XDF6hwJNBbYLuVspo03w5 +nCy5Z6r28j/PRn+D0ikGuvRbXbN8X1Cx89vEnnUVpdAtfUfJ5pVag/p6J2pakmzHc k/V+AhP42zscGFN8csMJ506cA5x/mPmtM2EEkY74= Date: Mon, 8 Jun 2020 11:41:48 -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: <20200608164148.GA1394249@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 08, 2020 at 10:54:15AM +0800, Zhangfei Gao wrote: > On 2020/6/6 上午7:19, Bjorn Helgaas wrote: > > 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? > > > Here the fake pci device has standard PCI cfg space, but physical > implementation is base on AMBA > They can provide pasid feature. > However, > 1, does not support tlp since they are not real pci devices. > 2. does not support pri, instead support stall (provided by smmu) > And stall is not a pci feature, so it is not described in struct pci_dev, > but in struct iommu_fwspec. > So we use this fixup to tell pci system that the devices can support stall, > and hereby support pasid. This did not answer my question. Are you proposing that we update a quirk every time a new AMBA device is released? I don't think that would be a good model.