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authorDavid Woodhouse <David.Woodhouse@intel.com>2016-02-15 12:42:38 +0000
committerDavid Woodhouse <David.Woodhouse@intel.com>2016-02-15 12:42:38 +0000
commit46924008273ed03bd11dbb32136e3da4cfe056e1 (patch)
tree9d77cb792ac4ccf28aa687942d1c6f1adaf5dd67 /drivers/iommu
parentfda3bec12d0979aae3f02ee645913d66fbc8a26e (diff)
downloadlinux-46924008273ed03bd11dbb32136e3da4cfe056e1.tar.bz2
iommu/vt-d: Clear PPR bit to ensure we get more page request interrupts
According to the VT-d specification we need to clear the PPR bit in the Page Request Status register when handling page requests, or the hardware won't generate any more interrupts. This wasn't actually necessary on SKL/KBL (which may well be the subject of a hardware erratum, although it's harmless enough). But other implementations do appear to get it right, and we only ever get one interrupt unless we clear the PPR bit. Reported-by: CQ Tang <cq.tang@intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> Cc: stable@vger.kernel.org
Diffstat (limited to 'drivers/iommu')
-rw-r--r--drivers/iommu/intel-svm.c4
1 files changed, 4 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) {