linux-kernel - [patch 02/22] PCI/MSI: Fix pci_irq_vector()/pci_irq_get

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Date:   Sat, 27 Nov 2021 02:19:23 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Bjorn Helgaas <helgaas@...nel.org>, Marc Zygnier <maz@...nel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Megha Dey <megha.dey@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, linux-pci@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        linuxppc-dev@...ts.ozlabs.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        sparclinux@...r.kernel.org, x86@...nel.org,
        xen-devel@...ts.xenproject.org, ath11k@...ts.infradead.org,
        Wei Liu <wei.liu@...nel.org>, linux-hyperv@...r.kernel.org,
        Juergen Gross <jgross@...e.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>
Subject: [patch 02/22] PCI/MSI: Fix pci_irq_vector()/pci_irq_get_attinity()

pci_irq_vector() and pci_irq_get_affinity() use the list position to find the
MSI-X descriptor at a given index. That's correct for the normal case where
the entry number is the same as the list position.

But it's wrong for cases where MSI-X was allocated with an entries array
describing sparse entry numbers into the hardware message descriptor
table. That's inconsistent at best.

Make it always check the entry number because that's what the zero base
index really means. This change won't break existing users which use a
sparse entries array for allocation because these users retrieve the Linux
interrupt number from the entries array after allocation and none of them
uses pci_irq_vector() or pci_irq_get_affinity().

Fixes: aff171641d18 ("PCI: Provide sensible IRQ vector alloc/free routines")
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 drivers/pci/msi.c |   26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1187,19 +1187,24 @@ EXPORT_SYMBOL(pci_free_irq_vectors);
 
 /**
  * pci_irq_vector - return Linux IRQ number of a device vector
- * @dev: PCI device to operate on
- * @nr: device-relative interrupt vector index (0-based).
+ * @dev:	PCI device to operate on
+ * @nr:		Interrupt vector index (0-based)
+ *
+ * @nr has the following meanings depending on the interrupt mode:
+ *   MSI-X:	The index in the MSI-X vector table
+ *   MSI:	The index of the enabled MSI vectors
+ *   INTx:	Must be 0
+ *
+ * Return: The Linux interrupt number or -EINVAl if @nr is out of range.
  */
 int pci_irq_vector(struct pci_dev *dev, unsigned int nr)
 {
 	if (dev->msix_enabled) {
 		struct msi_desc *entry;
-		int i = 0;
 
 		for_each_pci_msi_entry(entry, dev) {
-			if (i == nr)
+			if (entry->msi_attrib.entry_nr == nr)
 				return entry->irq;
-			i++;
 		}
 		WARN_ON_ONCE(1);
 		return -EINVAL;
@@ -1223,17 +1228,22 @@ EXPORT_SYMBOL(pci_irq_vector);
  * pci_irq_get_affinity - return the affinity of a particular MSI vector
  * @dev:	PCI device to operate on
  * @nr:		device-relative interrupt vector index (0-based).
+ *
+ * @nr has the following meanings depending on the interrupt mode:
+ *   MSI-X:	The index in the MSI-X vector table
+ *   MSI:	The index of the enabled MSI vectors
+ *   INTx:	Must be 0
+ *
+ * Return: A cpumask pointer or NULL if @nr is out of range
  */
 const struct cpumask *pci_irq_get_affinity(struct pci_dev *dev, int nr)
 {
 	if (dev->msix_enabled) {
 		struct msi_desc *entry;
-		int i = 0;
 
 		for_each_pci_msi_entry(entry, dev) {
-			if (i == nr)
+			if (entry->msi_attrib.entry_nr == nr)
 				return &entry->affinity->mask;
-			i++;
 		}
 		WARN_ON_ONCE(1);
 		return NULL;