linux-kernel - [PATCHv4 2/2] iommu/vt-d: Limit number of faults to clear in irq handler

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Date:   Sat, 31 Mar 2018 01:33:12 +0100
From:   Dmitry Safonov <dima@...sta.com>
To:     linux-kernel@...r.kernel.org, joro@...tes.org
Cc:     0x7f454c46@...il.com, Dmitry Safonov <dima@...sta.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        iommu@...ts.linux-foundation.org
Subject: [PATCHv4 2/2] iommu/vt-d: Limit number of faults to clear in irq handler

Theoretically, on some machines faults might be generated faster than
they're cleared by CPU. Let's limit the cleaning-loop by number of hw
fault registers.

Cc: Alex Williamson <alex.williamson@...hat.com>
Cc: David Woodhouse <dwmw2@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Joerg Roedel <joro@...tes.org>
Cc: Lu Baolu <baolu.lu@...ux.intel.com>
Cc: iommu@...ts.linux-foundation.org
Signed-off-by: Dmitry Safonov <dima@...sta.com>
---
 drivers/iommu/dmar.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index 6c4ea32ee6a9..cf1105111209 100644
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -1615,7 +1615,7 @@ static int dmar_fault_do_one(struct intel_iommu *iommu, int type,
 irqreturn_t dmar_fault(int irq, void *dev_id)
 {
 	struct intel_iommu *iommu = dev_id;
-	int reg, fault_index;
+	int reg, fault_index, i;
 	u32 fault_status;
 	unsigned long flag;
 	static DEFINE_RATELIMIT_STATE(rs,
@@ -1633,7 +1633,7 @@ irqreturn_t dmar_fault(int irq, void *dev_id)
 
 	fault_index = dma_fsts_fault_record_index(fault_status);
 	reg = cap_fault_reg_offset(iommu->cap);
-	while (1) {
+	for (i = 0; i < cap_num_fault_regs(iommu->cap); i++) {
 		/* Disable printing, simply clear the fault when ratelimited */
 		bool ratelimited = !__ratelimit(&rs);
 		u8 fault_reason;
-- 
2.13.6