From: Lu Baolu <baolu.lu@linux.intel.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: Kan Liang <kan.liang@linux.intel.com>,
Lu Baolu <baolu.lu@linux.intel.com>,
iommu@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: [PATCH 1/3] iommu/vt-d: Remove unnecessary locking in intel_irq_remapping_alloc()
Date: Wed, 29 Mar 2023 21:47:19 +0800 [thread overview]
Message-ID: <20230329134721.469447-2-baolu.lu@linux.intel.com> (raw)
In-Reply-To: <20230329134721.469447-1-baolu.lu@linux.intel.com>
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 <jacob.jun.pan@linux.intel.com>
Tested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20230314051836.23817-1-baolu.lu@linux.intel.com
---
drivers/iommu/intel/irq_remapping.c | 6 ------
1 file changed, 6 deletions(-)
diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c
index 6d01fa078c36..df9e261af0b5 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);
--
2.34.1
next prev parent reply other threads:[~2023-03-29 13:47 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-29 13:47 [PATCH 0/3] [PULL REQUEST] iommu/vt-d: Fixes for v6.3-rc4 Lu Baolu
2023-03-29 13:47 ` Lu Baolu [this message]
2023-03-29 13:47 ` [PATCH 2/3] iommu/vt-d: Allow zero SAGAW if second-stage not supported Lu Baolu
2023-03-29 13:47 ` [PATCH 3/3] iommu/vt-d: Fix an IOMMU perfmon warning when CPU hotplug Lu Baolu
2023-03-31 8:06 ` [PATCH 0/3] [PULL REQUEST] iommu/vt-d: Fixes for v6.3-rc4 Joerg Roedel
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