linux-kernel - [PATCH 1/3] iommu/vt-d: Add rate limited information when PRQ overflows

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Date:   Thu, 21 Jan 2021 09:45:03 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>
Cc:     Ashok Raj <ashok.raj@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH 1/3] iommu/vt-d: Add rate limited information when PRQ overflows

So that the uses could get chances to know what happened.

Suggested-by: Ashok Raj <ashok.raj@...el.com>
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/iommu/intel/svm.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index 033b25886e57..f49fe715477b 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -895,6 +895,7 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 	struct intel_iommu *iommu = d;
 	struct intel_svm *svm = NULL;
 	int head, tail, handled = 0;
+	struct page_req_dsc *req;
 
 	/* Clear PPR bit before reading head/tail registers, to
 	 * ensure that we get a new interrupt if needed. */
@@ -904,7 +905,6 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 	head = dmar_readq(iommu->reg + DMAR_PQH_REG) & PRQ_RING_MASK;
 	while (head != tail) {
 		struct vm_area_struct *vma;
-		struct page_req_dsc *req;
 		struct qi_desc resp;
 		int result;
 		vm_fault_t ret;
@@ -1042,8 +1042,14 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 	 * Clear the page request overflow bit and wake up all threads that
 	 * are waiting for the completion of this handling.
 	 */
-	if (readl(iommu->reg + DMAR_PRS_REG) & DMA_PRS_PRO)
+	if (readl(iommu->reg + DMAR_PRS_REG) & DMA_PRS_PRO) {
+		head = dmar_readq(iommu->reg + DMAR_PQH_REG) & PRQ_RING_MASK;
+		req = &iommu->prq[head / sizeof(*req)];
+		pr_warn_ratelimited("IOMMU: %s: Page request overflow: HEAD: %08llx %08llx",
+				    iommu->name, ((unsigned long long *)req)[0],
+				    ((unsigned long long *)req)[1]);
 		writel(DMA_PRS_PRO, iommu->reg + DMAR_PRS_REG);
+	}
 
 	if (!completion_done(&iommu->prq_complete))
 		complete(&iommu->prq_complete);
-- 
2.25.1