2 files changed, 7 insertions, 0 deletions

diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index 97a818992d6d..d9939fa9b588 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -524,6 +524,10 @@ static irqreturn_t prq_event_thread(int irq, void *d)
         struct intel_svm *svm = NULL;
         int head, tail, handled = 0;
 
+        /* Clear PPR bit before reading head/tail registers, to
+         * ensure that we get a new interrupt if needed. */
+        writel(DMA_PRS_PPR, iommu->reg + DMAR_PRS_REG);
+
         tail = dmar_readq(iommu->reg + DMAR_PQT_REG) & PRQ_RING_MASK;
         head = dmar_readq(iommu->reg + DMAR_PQH_REG) & PRQ_RING_MASK;
         while (head != tail) {
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index 821273ca4873..2d9b650047a5 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -235,6 +235,9 @@ static inline void dmar_writeq(void __iomem *addr, u64 val)
 /* low 64 bit */
 #define dma_frcd_page_addr(d) (d & (((u64)-1) << PAGE_SHIFT))
 
+/* PRS_REG */
+#define DMA_PRS_PPR     ((u32)1)
+
 #define IOMMU_WAIT_OP(iommu, offset, op, cond, sts)                     \
 do {                                                                    \
         cycles_t start_time = get_cycles();                             \