From 5fec945105448b958b8418b7e5d043d630ec3155 Mon Sep 17 00:00:00 2001 From: Alexander Gordeev Date: Mon, 13 May 2013 11:06:17 +0200 Subject: [PATCH] x86/MSI: Conserve interrupt resources when using multiple-MSIs Current multiple-MSI implementation does not take into account actual number of requested MSIs and always rounds that number to a larger power-of-two value. Yet, the number of MSIs a PCI device could send (and therefore the number of messages a device driver could request) may be smaller. As result, resources allocated for extra MSIs are just wasted. This update takes advantage of 'msi_desc::nvec_used' field introduced with generic MSI code to track the 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 conserved IRTEs, but Jan noticed that a malfunctioning PCI device might send a message number it did not claim and thus refer to an IRTE it does not own. To avoid this security hole, as many IRTEs are reserved as the device could possibly send. [bhelgaas: changelog, rename to "nvec_used"] Signed-off-by: Alexander Gordeev Signed-off-by: Bjorn Helgaas --- drivers/iommu/irq_remapping.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c index dcfea4e39be7..39f81aeefcd6 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_used); 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_used = 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_used = 0; msidesc->msi_attrib.multiple = 0; return ret; -- 2.39.5