Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752020Ab3EMJFE (ORCPT ); Mon, 13 May 2013 05:05:04 -0400 Received: from mx1.redhat.com ([209.132.183.28]:63289 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750704Ab3EMJFB (ORCPT ); Mon, 13 May 2013 05:05:01 -0400 Date: Mon, 13 May 2013 11:06:17 +0200 From: Alexander Gordeev To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, linux-pci@vger.kernel.org, Suresh Siddha , Yinghai Lu , Joerg Roedel , Jan Beulich , Ingo Molnar , Bjorn Helgaas Subject: [PATCH v3 -tip x86/apic 2/2] x86/MSI: Conserve interrupt resources when using multiple-MSIs Message-ID: <924d05fe41fb93fdc2013680fb220d4b171de303.1368431413.git.agordeev@redhat.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2824 Lines: 81 Current multiple-MSI implementation does not take into account actual number of requested MSIs and always rounds that number to a closest power-of-two value. Yet, a number of MSIs a PCI device could send (and therefore a number of messages a device driver could request) may be a lesser power-of-two. As result, resources allocated for extra MSIs just wasted. This update takes advantage of 'msi_desc::nvec' field introduced with generic MSI code to track number of requested and used MSIs. As result, resources associated with interrupts are conserved. Of those resources most noticeable are x86 interrupt vectors. The initial version of this fix also consumed on IRTEs, but Jan noticed that a malfunctioning PCI device might send a message number it did not claim and thus refer an IRTE it does not own. To avoid this security hole the old-way approach preserved and as many IRTEs are reserved as the device could possibly send. Signed-off-by: Alexander Gordeev --- drivers/iommu/irq_remapping.c | 12 +++++++----- 1 files changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c index d56f8c1..9eeb6cf 100644 --- a/drivers/iommu/irq_remapping.c +++ b/drivers/iommu/irq_remapping.c @@ -51,26 +51,27 @@ static void irq_remapping_disable_io_apic(void) static int do_setup_msi_irqs(struct pci_dev *dev, int nvec) { - int node, ret, sub_handle, index = 0; + int node, ret, sub_handle, nvec_pow2, index = 0; unsigned int irq; struct msi_desc *msidesc; - nvec = __roundup_pow_of_two(nvec); - WARN_ON(!list_is_singular(&dev->msi_list)); msidesc = list_entry(dev->msi_list.next, struct msi_desc, list); WARN_ON(msidesc->irq); WARN_ON(msidesc->msi_attrib.multiple); + WARN_ON(msidesc->nvec); node = dev_to_node(&dev->dev); irq = __create_irqs(get_nr_irqs_gsi(), nvec, node); if (irq == 0) return -ENOSPC; - msidesc->msi_attrib.multiple = ilog2(nvec); + nvec_pow2 = __roundup_pow_of_two(nvec); + msidesc->nvec = nvec; + msidesc->msi_attrib.multiple = ilog2(nvec_pow2); for (sub_handle = 0; sub_handle < nvec; sub_handle++) { if (!sub_handle) { - index = msi_alloc_remapped_irq(dev, irq, nvec); + index = msi_alloc_remapped_irq(dev, irq, nvec_pow2); if (index < 0) { ret = index; goto error; @@ -95,6 +96,7 @@ error: * IRQs from tearing down again in default_teardown_msi_irqs() */ msidesc->irq = 0; + msidesc->nvec = 0; msidesc->msi_attrib.multiple = 0; return ret; -- 1.7.7.6 -- Regards, Alexander Gordeev agordeev@redhat.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/