[PATCH 1/2] iommu/vt-d: Fix intel iommu iotlb sync hardlockup and retry

[Lu Baolu <baolu.lu@linux.intel.com>]

From: Guanghui Feng <guanghuifeng@linux.alibaba.com>

During the qi_check_fault process after an IOMMU ITE event, requests at
odd-numbered positions in the queue are set to QI_ABORT, only satisfying
single-request submissions. However, qi_submit_sync now supports multiple
simultaneous submissions, and can't guarantee that the wait_desc will be
at an odd-numbered position. Therefore, if an item times out, IOMMU can't
re-initiate the request, resulting in an infinite polling wait.

This modifies the process by setting the status of all requests already
fetched by IOMMU and recorded as QI_IN_USE status (including wait_desc
requests) to QI_ABORT, thus enabling multiple requests to be resubmitted.

Fixes: 8a1d82462540 ("iommu/vt-d: Multiple descriptors per qi_submit_sync()")
Cc: stable@vger.kernel.org
Signed-off-by: Guanghui Feng <guanghuifeng@linux.alibaba.com>
Tested-by: Shuai Xue <xueshuai@linux.alibaba.com>
Reviewed-by: Shuai Xue <xueshuai@linux.alibaba.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Link: https://lore.kernel.org/r/20260306101516.3885775-1-guanghuifeng@linux.alibaba.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/iommu/intel/dmar.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index d68c06025cac..69222dbd2af0 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -1314,7 +1314,6 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index)
 	if (fault & DMA_FSTS_ITE) {
 		head = readl(iommu->reg + DMAR_IQH_REG);
 		head = ((head >> shift) - 1 + QI_LENGTH) % QI_LENGTH;
-		head |= 1;
 		tail = readl(iommu->reg + DMAR_IQT_REG);
 		tail = ((tail >> shift) - 1 + QI_LENGTH) % QI_LENGTH;
 
@@ -1331,7 +1330,7 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index)
 		do {
 			if (qi->desc_status[head] == QI_IN_USE)
 				qi->desc_status[head] = QI_ABORT;
-			head = (head - 2 + QI_LENGTH) % QI_LENGTH;
+			head = (head - 1 + QI_LENGTH) % QI_LENGTH;
 		} while (head != tail);
 
 		/*
-- 
2.43.0