From patchwork Thu Jan 3 22:50:32 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Keith Busch X-Patchwork-Id: 1020544 X-Patchwork-Delegate: bhelgaas@google.com Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=intel.com Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 43W39C1bMKz9s9G for ; Fri, 4 Jan 2019 09:53:03 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728683AbfACWxC (ORCPT ); Thu, 3 Jan 2019 17:53:02 -0500 Received: from mga02.intel.com ([134.134.136.20]:61366 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726529AbfACWxB (ORCPT ); Thu, 3 Jan 2019 17:53:01 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Jan 2019 14:53:01 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,436,1539673200"; d="scan'208";a="307303409" Received: from unknown (HELO localhost.lm.intel.com) ([10.232.112.69]) by fmsmga006.fm.intel.com with ESMTP; 03 Jan 2019 14:53:00 -0800 From: Keith Busch To: Jens Axboe , Christoph Hellwig , Sagi Grimberg , Ming Lei , linux-nvme@lists.infradead.org, Bjorn Helgaas , linux-pci@vger.kernel.org Cc: Keith Busch Subject: [PATCHv2 3/4] PCI/MSI: Handle vector reduce and retry Date: Thu, 3 Jan 2019 15:50:32 -0700 Message-Id: <20190103225033.11249-4-keith.busch@intel.com> X-Mailer: git-send-email 2.13.6 In-Reply-To: <20190103225033.11249-1-keith.busch@intel.com> References: <20190103225033.11249-1-keith.busch@intel.com> Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org The struct irq_affinity nr_sets forced the driver to handle reducing the vector count on allocation failures because the set distribution counts are driver specific. The change to this API requires very different usage than before, and introduced new error corner cases that weren't being handled. It is also less efficient since the driver doesn't actually know what a proper vector count it should use since it only sees the error code and can only reduce by one instead of going straight to a possible vector count like PCI is able to do. Provide a driver specific callback for managed irq set creation so that PCI can take a min and max vectors as before to handle the reduce and retry logic. The usage is not particularly obvious for this new feature, so append documentation for driver usage. Signed-off-by: Keith Busch --- Documentation/PCI/MSI-HOWTO.txt | 36 +++++++++++++++++++++++++++++++++++- drivers/pci/msi.c | 20 ++++++-------------- include/linux/interrupt.h | 5 +++++ 3 files changed, 46 insertions(+), 15 deletions(-) diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt index 618e13d5e276..391b1f369138 100644 --- a/Documentation/PCI/MSI-HOWTO.txt +++ b/Documentation/PCI/MSI-HOWTO.txt @@ -98,7 +98,41 @@ The flags argument is used to specify which type of interrupt can be used by the device and the driver (PCI_IRQ_LEGACY, PCI_IRQ_MSI, PCI_IRQ_MSIX). A convenient short-hand (PCI_IRQ_ALL_TYPES) is also available to ask for any possible kind of interrupt. If the PCI_IRQ_AFFINITY flag is set, -pci_alloc_irq_vectors() will spread the interrupts around the available CPUs. +pci_alloc_irq_vectors() will spread the interrupts around the available +CPUs. Vector affinities allocated under the PCI_IRQ_AFFINITY flag are +managed by the kernel, and are not tunable from user space like other +vectors. + +When your driver requires a more complex vector affinity configuration +than a default spread of all vectors, the driver may use the following +function: + + int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs, + unsigned int max_vecs, unsigned int flags, + const struct irq_affinity *affd); + +The 'struct irq_affinity *affd' allows a driver to specify additional +characteristics for how a driver wants the vector management to occur. The +'pre_vectors' and 'post_vectors' fields define how many vectors the driver +wants to not participate in kernel managed affinities, and whether those +special vectors are at the beginning or the end of the vector space. + +It may also be the case that a driver wants multiple sets of fully +affinitized vectors. For example, a single PCI function may provide +different high performance services that want full CPU affinity for each +service independent of other services. In this case, the driver may use +the struct irq_affinity's 'nr_sets' field to specify how many groups of +vectors need to be spread across all the CPUs, and fill in the 'sets' +array to say how many vectors the driver wants in each set. + +When using multiple affinity 'sets', the error handling for vector +reduction and retry becomes more complicated since the PCI core +doesn't know how to redistribute the vector count across the sets. In +order to provide this error handling, the driver must also provide the +'recalc_sets()' callback and set the 'priv' data needed for the driver +specific vector distribution. The driver's callback is responsible to +ensure the sum of the vector counts across its sets matches the new +vector count that PCI can allocate. To get the Linux IRQ numbers passed to request_irq() and free_irq() and the vectors, use the following function: diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c index 7a1c8a09efa5..b93ac49be18d 100644 --- a/drivers/pci/msi.c +++ b/drivers/pci/msi.c @@ -1035,13 +1035,6 @@ static int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec, if (maxvec < minvec) return -ERANGE; - /* - * If the caller is passing in sets, we can't support a range of - * vectors. The caller needs to handle that. - */ - if (affd && affd->nr_sets && minvec != maxvec) - return -EINVAL; - if (WARN_ON_ONCE(dev->msi_enabled)) return -EINVAL; @@ -1061,6 +1054,9 @@ static int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec, return -ENOSPC; } + if (nvec != maxvec && affd && affd->recalc_sets) + affd->recalc_sets((struct irq_affinity *)affd, nvec); + rc = msi_capability_init(dev, nvec, affd); if (rc == 0) return nvec; @@ -1093,13 +1089,6 @@ static int __pci_enable_msix_range(struct pci_dev *dev, if (maxvec < minvec) return -ERANGE; - /* - * If the caller is passing in sets, we can't support a range of - * supported vectors. The caller needs to handle that. - */ - if (affd && affd->nr_sets && minvec != maxvec) - return -EINVAL; - if (WARN_ON_ONCE(dev->msix_enabled)) return -EINVAL; @@ -1110,6 +1099,9 @@ static int __pci_enable_msix_range(struct pci_dev *dev, return -ENOSPC; } + if (nvec != maxvec && affd && affd->recalc_sets) + affd->recalc_sets((struct irq_affinity *)affd, nvec); + rc = __pci_enable_msix(dev, entries, nvec, affd); if (rc == 0) return nvec; diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index c672f34235e7..01c06829ff43 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -249,12 +249,17 @@ struct irq_affinity_notify { * the MSI(-X) vector space * @nr_sets: Length of passed in *sets array * @sets: Number of affinitized sets + * @recalc_sets: Recalculate sets if the previously requested allocation + * failed + * @priv: Driver private data */ struct irq_affinity { int pre_vectors; int post_vectors; int nr_sets; int *sets; + void (*recalc_sets)(struct irq_affinity *, unsigned int); + void *priv; }; /**