linux-kernel - [PATCH] iommu/vt-d: fix system hang on reboot -f

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Message-Id: <20250220101511.37602-1-cuiyunhui@bytedance.com>
Date: Thu, 20 Feb 2025 18:15:11 +0800
From: Yunhui Cui <cuiyunhui@...edance.com>
To: dwmw2@...radead.org,
	baolu.lu@...ux.intel.com,
	joro@...tes.org,
	will@...nel.org,
	robin.murphy@....com,
	iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Cc: Yunhui Cui <cuiyunhui@...edance.com>
Subject: [PATCH] iommu/vt-d: fix system hang on reboot -f

When entering intel_iommu_shutdown, system interrupts are disabled,
and the reboot process might be scheduled out by down_write(). If the
scheduled process does not yield (e.g., while(1)), the system will hang.

Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
---
 drivers/iommu/intel/iommu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index cc46098f875b..76a1d83b46bf 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -2871,7 +2871,8 @@ void intel_iommu_shutdown(void)
 	if (no_iommu || dmar_disabled)
 		return;
 
-	down_write(&dmar_global_lock);
+	if (!down_write_trylock(&dmar_global_lock))
+		return;
 
 	/* Disable PMRs explicitly here. */
 	for_each_iommu(iommu, drhd)
-- 
2.39.2