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From:   Thomas Gleixner <tglx@linutronix.de>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     "Surendrakumar Upadhyay, TejaskumarX" 
        <tejaskumarx.surendrakumar.upadhyay@intel.com>,
        "Meena, Mahesh" <mahesh.meena@intel.com>,
        linux-pci@vger.kernel.org, Bjorn Helgaas <helgaas@kernel.org>,
        Krzysztof Wilczynski <kw@linux.com>,
        Marc Zyngier <maz@kernel.org>
Subject: [PATCH] PCI: vmd: Prevent recursive locking on interrupt allocation
Date:   Sun, 13 Feb 2022 14:54:05 +0100
Message-ID: <87a6euub2a.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Tejas reported the following recursive locking issue:

 swapper/0/1 is trying to acquire lock:
 ffff8881074fd0a0 (&md->mutex){+.+.}-{3:3}, at: msi_get_virq+0x30/0xc0
 
 but task is already holding lock:
 ffff8881017cd6a0 (&md->mutex){+.+.}-{3:3}, at: __pci_enable_msi_range+0xf2/0x290
 
 stack backtrace:
  __mutex_lock+0x9d/0x920
  msi_get_virq+0x30/0xc0
  pci_irq_vector+0x26/0x30
  vmd_msi_init+0xcc/0x210
  msi_domain_alloc+0xbf/0x150
  msi_domain_alloc_irqs_descs_locked+0x3e/0xb0
  __pci_enable_msi_range+0x155/0x290
  pci_alloc_irq_vectors_affinity+0xba/0x100
  pcie_port_device_register+0x307/0x550
  pcie_portdrv_probe+0x3c/0xd0
  pci_device_probe+0x95/0x110

This is caused by the VMD MSI code which does a lookup of the Linux
interrupt number for an VMD managed MSI[X] vector. The lookup function
tries to acquire the already held mutex.

Avoid that by caching the Linux interrupt number at initialization time
instead of looking it up over and over.

Fixes: 82ff8e6b78fc ("PCI/MSI: Use msi_get_virq() in pci_get_vector()")
Reported-by: "Surendrakumar Upadhyay, TejaskumarX" <tejaskumarx.surendrakumar.upadhyay@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 drivers/pci/controller/vmd.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- a/drivers/pci/controller/vmd.c
+++ b/drivers/pci/controller/vmd.c
@@ -99,11 +99,13 @@ struct vmd_irq {
  * @srcu:	SRCU struct for local synchronization.
  * @count:	number of child IRQs assigned to this vector; used to track
  *		sharing.
+ * @virq:	The underlying VMD Linux interrupt number
  */
 struct vmd_irq_list {
 	struct list_head	irq_list;
 	struct srcu_struct	srcu;
 	unsigned int		count;
+	unsigned int		virq;
 };
 
 struct vmd_dev {
@@ -253,7 +255,6 @@ static int vmd_msi_init(struct irq_domai
 	struct msi_desc *desc = arg->desc;
 	struct vmd_dev *vmd = vmd_from_bus(msi_desc_to_pci_dev(desc)->bus);
 	struct vmd_irq *vmdirq = kzalloc(sizeof(*vmdirq), GFP_KERNEL);
-	unsigned int index, vector;
 
 	if (!vmdirq)
 		return -ENOMEM;
@@ -261,10 +262,8 @@ static int vmd_msi_init(struct irq_domai
 	INIT_LIST_HEAD(&vmdirq->node);
 	vmdirq->irq = vmd_next_irq(vmd, desc);
 	vmdirq->virq = virq;
-	index = index_from_irqs(vmd, vmdirq->irq);
-	vector = pci_irq_vector(vmd->dev, index);
 
-	irq_domain_set_info(domain, virq, vector, info->chip, vmdirq,
+	irq_domain_set_info(domain, virq, vmdirq->irq->virq, info->chip, vmdirq,
 			    handle_untracked_irq, vmd, NULL);
 	return 0;
 }
@@ -685,7 +684,8 @@ static int vmd_alloc_irqs(struct vmd_dev
 			return err;
 
 		INIT_LIST_HEAD(&vmd->irqs[i].irq_list);
-		err = devm_request_irq(&dev->dev, pci_irq_vector(dev, i),
+		vmd->irqs[i].virq = pci_irq_vector(dev, i);
+		err = devm_request_irq(&dev->dev, vmd->irqs[i].virq,
 				       vmd_irq, IRQF_NO_THREAD,
 				       vmd->name, &vmd->irqs[i]);
 		if (err)
@@ -969,7 +969,7 @@ static int vmd_suspend(struct device *de
 	int i;
 
 	for (i = 0; i < vmd->msix_count; i++)
-		devm_free_irq(dev, pci_irq_vector(pdev, i), &vmd->irqs[i]);
+		devm_free_irq(dev, vmd->irqs[i].virq, &vmd->irqs[i]);
 
 	return 0;
 }
@@ -981,7 +981,7 @@ static int vmd_resume(struct device *dev
 	int err, i;
 
 	for (i = 0; i < vmd->msix_count; i++) {
-		err = devm_request_irq(dev, pci_irq_vector(pdev, i),
+		err = devm_request_irq(dev, vmd->irqs[i].virq,
 				       vmd_irq, IRQF_NO_THREAD,
 				       vmd->name, &vmd->irqs[i]);
 		if (err)