From: Lu Baolu Date: Wed, 29 Mar 2023 13:47:19 +0000 (+0800) Subject: iommu/vt-d: Remove unnecessary locking in intel_irq_remapping_alloc() X-Git-Tag: v6.6.17~5207^2~2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=c7d624520c1bd4e42d8ceb8283d6505fc90acccb;p=platform%2Fkernel%2Flinux-rpi.git iommu/vt-d: Remove unnecessary locking in intel_irq_remapping_alloc() The global rwsem dmar_global_lock was introduced by commit 3a5670e8ac932 ("iommu/vt-d: Introduce a rwsem to protect global data structures"). It is used to protect DMAR related global data from DMAR hotplug operations. Using dmar_global_lock in intel_irq_remapping_alloc() is unnecessary as the DMAR global data structures are not touched there. Remove it to avoid below lockdep warning. ====================================================== WARNING: possible circular locking dependency detected 6.3.0-rc2 #468 Not tainted ------------------------------------------------------ swapper/0/1 is trying to acquire lock: ff1db4cb40178698 (&domain->mutex){+.+.}-{3:3}, at: __irq_domain_alloc_irqs+0x3b/0xa0 but task is already holding lock: ffffffffa0c1cdf0 (dmar_global_lock){++++}-{3:3}, at: intel_iommu_init+0x58e/0x880 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (dmar_global_lock){++++}-{3:3}: lock_acquire+0xd6/0x320 down_read+0x42/0x180 intel_irq_remapping_alloc+0xad/0x750 mp_irqdomain_alloc+0xb8/0x2b0 irq_domain_alloc_irqs_locked+0x12f/0x2d0 __irq_domain_alloc_irqs+0x56/0xa0 alloc_isa_irq_from_domain.isra.7+0xa0/0xe0 mp_map_pin_to_irq+0x1dc/0x330 setup_IO_APIC+0x128/0x210 apic_intr_mode_init+0x67/0x110 x86_late_time_init+0x24/0x40 start_kernel+0x41e/0x7e0 secondary_startup_64_no_verify+0xe0/0xeb -> #0 (&domain->mutex){+.+.}-{3:3}: check_prevs_add+0x160/0xef0 __lock_acquire+0x147d/0x1950 lock_acquire+0xd6/0x320 __mutex_lock+0x9c/0xfc0 __irq_domain_alloc_irqs+0x3b/0xa0 dmar_alloc_hwirq+0x9e/0x120 iommu_pmu_register+0x11d/0x200 intel_iommu_init+0x5de/0x880 pci_iommu_init+0x12/0x40 do_one_initcall+0x65/0x350 kernel_init_freeable+0x3ca/0x610 kernel_init+0x1a/0x140 ret_from_fork+0x29/0x50 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(dmar_global_lock); lock(&domain->mutex); lock(dmar_global_lock); lock(&domain->mutex); *** DEADLOCK *** Fixes: 9dbb8e3452ab ("irqdomain: Switch to per-domain locking") Reviewed-by: Jacob Pan Tested-by: Jason Gunthorpe Signed-off-by: Lu Baolu Link: https://lore.kernel.org/r/20230314051836.23817-1-baolu.lu@linux.intel.com Link: https://lore.kernel.org/r/20230329134721.469447-2-baolu.lu@linux.intel.com Signed-off-by: Joerg Roedel --- diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c index 6d01fa0..df9e261 100644 --- a/drivers/iommu/intel/irq_remapping.c +++ b/drivers/iommu/intel/irq_remapping.c @@ -311,14 +311,12 @@ static int set_ioapic_sid(struct irte *irte, int apic) if (!irte) return -1; - down_read(&dmar_global_lock); for (i = 0; i < MAX_IO_APICS; i++) { if (ir_ioapic[i].iommu && ir_ioapic[i].id == apic) { sid = (ir_ioapic[i].bus << 8) | ir_ioapic[i].devfn; break; } } - up_read(&dmar_global_lock); if (sid == 0) { pr_warn("Failed to set source-id of IOAPIC (%d)\n", apic); @@ -338,14 +336,12 @@ static int set_hpet_sid(struct irte *irte, u8 id) if (!irte) return -1; - down_read(&dmar_global_lock); for (i = 0; i < MAX_HPET_TBS; i++) { if (ir_hpet[i].iommu && ir_hpet[i].id == id) { sid = (ir_hpet[i].bus << 8) | ir_hpet[i].devfn; break; } } - up_read(&dmar_global_lock); if (sid == 0) { pr_warn("Failed to set source-id of HPET block (%d)\n", id); @@ -1339,9 +1335,7 @@ static int intel_irq_remapping_alloc(struct irq_domain *domain, if (!data) goto out_free_parent; - down_read(&dmar_global_lock); index = alloc_irte(iommu, &data->irq_2_iommu, nr_irqs); - up_read(&dmar_global_lock); if (index < 0) { pr_warn("Failed to allocate IRTE\n"); kfree(data);