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 54D8AC433E0 for ; Mon, 1 Jun 2020 17:41:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 22738207DA for ; Mon, 1 Jun 2020 17:41:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591033268; bh=egFH6RgQ4a+4kLCfGrEDkjv5v4bJblqDQOjodPikqEM=; h=Date:From:To:Cc:Subject:In-Reply-To:List-ID:From; b=RIVmAK75cmgDVIrimRB4BmGk7O3SbS66iMPw95FcvdSsiFbgce8lJvgvInAPlHv6L +d8otOMUxlhOJQxpyzWtZCy1E3Q+tE53fvSpNXFo7BPEStCeTPzz233fx4dg4TmQgN OAm5+zLvsCLAX58/mq16QKb92HPBUMQP0NTVSkjc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727056AbgFARlH (ORCPT ); Mon, 1 Jun 2020 13:41:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:58534 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726017AbgFARlH (ORCPT ); Mon, 1 Jun 2020 13:41:07 -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 48FEF206A4; Mon, 1 Jun 2020 17:41:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591033266; bh=egFH6RgQ4a+4kLCfGrEDkjv5v4bJblqDQOjodPikqEM=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=PBS/XvI5mPBJhMQPW3QR/267YghZh8VBNHFVIA3y76nvmv7wSAOnIG8ZofBmrwL3W hjX/e/kbh6hI/0SHMT/KsCJ3IYwK/78zwY6ZY8W6ZDDtNYI4kfbVVgq5NF84Mj/Dz5 u9OiYWmcq6uvLgae6Udy20G6q8HsslAkBraLQcZo= Date: Mon, 1 Jun 2020 12:41:04 -0500 From: Bjorn Helgaas To: Joerg Roedel Cc: Zhangfei Gao , 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: <20200601174104.GA734973@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200528073344.GO5221@8bytes.org> Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org 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. Bjorn [1] https://lore.kernel.org/linux-pci/b1533fd5-1fae-7256-9597-36d3d5de9d2a@molgen.mpg.de/