From: Lu Baolu Date: Tue, 26 Jan 2021 08:07:29 +0000 (+0800) Subject: iommu/vt-d: Clear PRQ overflow only when PRQ is empty X-Git-Tag: accepted/tizen/unified/20230118.172025~7688^2~4^5~8 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=28a77185f1cd0650b664f54614143aaaa3a7a615;p=platform%2Fkernel%2Flinux-rpi.git iommu/vt-d: Clear PRQ overflow only when PRQ is empty It is incorrect to always clear PRO when it's set w/o first checking whether the overflow condition has been cleared. Current code assumes that if an overflow condition occurs it must have been cleared by earlier loop. However since the code runs in a threaded context, the overflow condition could occur even after setting the head to the tail under some extreme condition. To be sane, we should read both head/tail again when seeing a pending PRO and only clear PRO after all pending PRs have been handled. Suggested-by: Kevin Tian Signed-off-by: Lu Baolu Link: https://lore.kernel.org/linux-iommu/MWHPR11MB18862D2EA5BD432BF22D99A48CA09@MWHPR11MB1886.namprd11.prod.outlook.com/ Link: https://lore.kernel.org/r/20210126080730.2232859-2-baolu.lu@linux.intel.com Signed-off-by: Joerg Roedel --- diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c index 033b258..d7c98c5 100644 --- a/drivers/iommu/intel/svm.c +++ b/drivers/iommu/intel/svm.c @@ -1042,8 +1042,17 @@ prq_advance: * 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) - writel(DMA_PRS_PRO, iommu->reg + DMAR_PRS_REG); + if (readl(iommu->reg + DMAR_PRS_REG) & DMA_PRS_PRO) { + pr_info_ratelimited("IOMMU: %s: PRQ overflow detected\n", + iommu->name); + head = dmar_readq(iommu->reg + DMAR_PQH_REG) & PRQ_RING_MASK; + tail = dmar_readq(iommu->reg + DMAR_PQT_REG) & PRQ_RING_MASK; + if (head == tail) { + writel(DMA_PRS_PRO, iommu->reg + DMAR_PRS_REG); + pr_info_ratelimited("IOMMU: %s: PRQ overflow cleared", + iommu->name); + } + } if (!completion_done(&iommu->prq_complete)) complete(&iommu->prq_complete);