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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 E74E6C31E40 for ; Mon, 12 Aug 2019 17:58:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C01BF2075B for ; Mon, 12 Aug 2019 17:58:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726334AbfHLR6G (ORCPT ); Mon, 12 Aug 2019 13:58:06 -0400 Received: from mga07.intel.com ([134.134.136.100]:16540 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726090AbfHLR6G (ORCPT ); Mon, 12 Aug 2019 13:58:06 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Aug 2019 10:52:30 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,378,1559545200"; d="scan'208";a="376033949" Received: from megha-z97x-ud7-th.sc.intel.com ([143.183.85.162]) by fmsmga006.fm.intel.com with ESMTP; 12 Aug 2019 10:52:30 -0700 Message-ID: <1565633624.7042.23.camel@intel.com> Subject: Re: [RFC V1 RESEND 5/6] PCI/MSI: Free MSI-X resources by group From: Megha Dey To: Thomas Gleixner Cc: bhelgaas@google.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, marc.zyngier@arm.com, ashok.raj@intel.com, jacob.jun.pan@linux.intel.com Date: Mon, 12 Aug 2019 11:13:44 -0700 In-Reply-To: References: <1561162778-12669-1-git-send-email-megha.dey@linux.intel.com> <1561162778-12669-6-git-send-email-megha.dey@linux.intel.com> <1565118597.2401.116.camel@intel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.18.5.2-0ubuntu3.2 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Sun, 2019-08-11 at 09:18 +0200, Thomas Gleixner wrote: > On Tue, 6 Aug 2019, Megha Dey wrote: > > > > > On Sat, 2019-06-29 at 10:08 +0200, Thomas Gleixner wrote: > > > > > > Megha, > > > > > > On Fri, 21 Jun 2019, Megha Dey wrote: > > > > > > > > > > > > +static int free_msi_irqs_grp(struct pci_dev *dev, int > > > > group_id) > > > > +{ > > > > > > > > + > > > > + for_each_pci_msi_entry(entry, dev) { > > > > + if (entry->group_id == group_id && entry->irq) > > > > + for (i = 0; i < entry->nvec_used; i++) > > > > + BUG_ON(irq_has_action(entry- > > > > >irq + > > > > i)); > > > BUG_ON is wrong here. This can and must be handled gracefully. > > > > > Hmm, I reused this code from the 'free_msi_irqs' function. I am not > > sure why it is wrong to use BUG_ON here but ok to use it there, > > please > > let me know. > We are not adding BUG_ON() anymore except for situations where there > is > absolutely no way out. Just because there is still older code having > BUG_ON() does not make it any better. Copying it surely is no > justification. > > If there is really no way out, then you need to explain it. > Ok, got it. I will look into it closely to see if the BUG_ON is absolutely required. >   > > > > > > > > > > > > > +static void pci_msix_shutdown_grp(struct pci_dev *dev, int > > > > group_id) > > > > +{ > > > > + struct msi_desc *entry; > > > > + int grp_present = 0; > > > > + > > > > + if (pci_dev_is_disconnected(dev)) { > > > > + dev->msix_enabled = 0; > > > Huch? What's that? I can't figure out why this is needed and of > > > course it > > > completely lacks a comment explaining this.  > > > > > Again, I have reused this code from the pci_msix_shutdown() > > function. > > So for the group case, this is not required? > Copy and paste is not an argument, really. Can this happen here? If > so, > then please add a comment. > Ok, will do. > > > > > > > > > > > > > > > > > + return; > > > > + } > > > > + > > > > + /* Return the device with MSI-X masked as initial > > > > states > > > > */ > > > > + for_each_pci_msi_entry(entry, dev) { > > > > + if (entry->group_id == group_id) { > > > > + /* Keep cached states to be restored > > > > */ > > > > + __pci_msix_desc_mask_irq(entry, 1); > > > > + grp_present = 1; > > > > + } > > > > + } > > > > + > > > > + if (!grp_present) { > > > > + pci_err(dev, "Group to be disabled not > > > > present\n"); > > > > + return; > > > So you print an error and silently return > > > > > This is a void function, hence no error value can be returned. What > > do > > you think is the right thing to do if someone wants to delete a > > group > > which is not present? > Well, you made it a void function.  ok sure, got your point. >   > > > > > > > > > > > > > > > > > + } > > > > +} > > > > + > > > > +int pci_disable_msix_grp(struct pci_dev *dev, int group_id) > > > > +{ > > > > + int num_vecs; > > > > + > > > > + if (!pci_msi_enable || !dev) > > > > + return -EINVAL; > > > > + > > > > + pci_msix_shutdown_grp(dev, group_id); > > > > + num_vecs = free_msi_irqs_grp(dev, group_id); > > > just to call in another function which has to do the same > > > group_id > > > lookup > > > muck again. > > Even with the new proposal, we are to have 2 sets of functions: one > > to > > delete all the msic_desc entries associated with the device, and > > the > > other to delete those only belonging a 'user specified' group. So > > we do > > need to pass a group_id to these functions right? Yes, internally > > the > > deletion would be straightforward with the new approach. > That does not matter. If pci_msix_shutdown_grp() does not find a > group, why > proceeding instead of having a proper error return and telling the > caller? > Oh ok, I got it now, I will return a proper error code in the pci_msi_shutdown_grp and do the free_msi_irqs_grp only if the group is found. > Thanks, > > tglx