Messages in this thread Patch in this message | | | From | Lu Baolu <> | Subject | [PATCH 2/2] iommu/vt-d: Use rcu_lock in get_resv_regions | Date | Tue, 27 Sep 2022 13:31:09 +0800 |
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Commit 5f64ce5411b46 ("iommu/vt-d: Duplicate iommu_resv_region objects per device list") converted rcu_lock in get_resv_regions to dmar_global_lock to allow sleeping in iommu_alloc_resv_region(). This introduced possible recursive locking if get_resv_regions is called from within a section where intel_iommu_init() already holds dmar_global_lock.
Especially after commit c919739ce4721 ("iommu/vt-d: Handle race between registration and device probe"), below lockdep splats could always be seen.
============================================ WARNING: possible recursive locking detected 6.0.0-rc4+ #325 Tainted: G I -------------------------------------------- swapper/0/1 is trying to acquire lock: ffffffffa8a18c90 (dmar_global_lock){++++}-{3:3}, at: intel_iommu_get_resv_regions+0x25/0x270
but task is already holding lock: ffffffffa8a18c90 (dmar_global_lock){++++}-{3:3}, at: intel_iommu_init+0x36d/0x6ea
...
Call Trace: <TASK> dump_stack_lvl+0x48/0x5f __lock_acquire.cold.73+0xad/0x2bb lock_acquire+0xc2/0x2e0 ? intel_iommu_get_resv_regions+0x25/0x270 ? lock_is_held_type+0x9d/0x110 down_read+0x42/0x150 ? intel_iommu_get_resv_regions+0x25/0x270 intel_iommu_get_resv_regions+0x25/0x270 iommu_create_device_direct_mappings.isra.28+0x8d/0x1c0 ? iommu_get_dma_cookie+0x6d/0x90 bus_iommu_probe+0x19f/0x2e0 iommu_device_register+0xd4/0x130 intel_iommu_init+0x3e1/0x6ea ? iommu_setup+0x289/0x289 ? rdinit_setup+0x34/0x34 pci_iommu_init+0x12/0x3a do_one_initcall+0x65/0x320 ? rdinit_setup+0x34/0x34 ? rcu_read_lock_sched_held+0x5a/0x80 kernel_init_freeable+0x28a/0x2f3 ? rest_init+0x1b0/0x1b0 kernel_init+0x1a/0x130 ret_from_fork+0x1f/0x30 </TASK>
This rolls back dmar_global_lock to rcu_lock to avoid the lockdep splat.
Fixes: c919739ce4721 ("iommu/vt-d: Handle race between registration and device probe") Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> --- drivers/iommu/intel/iommu.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index d5965b4f8b60..b3cf0f991e29 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -4534,7 +4534,7 @@ static void intel_iommu_get_resv_regions(struct device *device, struct device *i_dev; int i; - down_read(&dmar_global_lock); + rcu_read_lock(); for_each_rmrr_units(rmrr) { for_each_active_dev_scope(rmrr->devices, rmrr->devices_cnt, i, i_dev) { @@ -4553,14 +4553,14 @@ static void intel_iommu_get_resv_regions(struct device *device, resv = iommu_alloc_resv_region(rmrr->base_address, length, prot, type, - GFP_KERNEL); + GFP_ATOMIC); if (!resv) break; list_add_tail(&resv->list, head); } } - up_read(&dmar_global_lock); + rcu_read_unlock(); #ifdef CONFIG_INTEL_IOMMU_FLOPPY_WA if (dev_is_pci(device)) { -- 2.34.1
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