iommu/amd: move wait_on_sem() out of spinlock

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[ Upstream commit d2a0cac105 ]

With iommu.strict=1, the existing completion wait path can cause soft
lockups under stressed environment, as wait_on_sem() busy-waits under the
spinlock with interrupts disabled.

Move the completion wait in iommu_completion_wait() out of the spinlock.
wait_on_sem() only polls the hardware-updated cmd_sem and does not require
iommu->lock, so holding the lock during the busy wait unnecessarily
increases contention and extends the time with interrupts disabled.

Signed-off-by: Ankit Soni <Ankit.Soni@amd.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Ankit Soni 2025-12-01 14:39:40 +00:00 • committed by Sasha Levin

parent 3308c7504e

commit e15768e688

1 changed files with 17 additions and 8 deletions

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drivers/iommu/amd/iommu.c

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