[PATCH 3.16 006/305] iommu/vt-d: Ratelimit fault handler

Ben Hutchings
2016-08-14T11:20:36Z

From: Alex Williamson <alex.williamson@redhat.com>

commit c43fce4eebae257ca413733690e2076757282093 upstream.

Fault rates can easily overwhelm the console and make the system
unresponsive. Ratelimit to allow an opportunity for maintenance.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Fixes: 0ac2491f57af ('x86, dmar: move page fault handling code to dmar.c')
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/iommu/dmar.c | 33 ++++++++++++++++++++++-----------
1 file changed, 22 insertions(+), 11 deletions(-)

--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -1482,10 +1482,17 @@ irqreturn_t dmar_fault(int irq, void *de
int reg, fault_index;
u32 fault_status;
unsigned long flag;
+ bool ratelimited;
+ static DEFINE_RATELIMIT_STATE(rs,
+ DEFAULT_RATELIMIT_INTERVAL,
+ DEFAULT_RATELIMIT_BURST);
+
+ /* Disable printing, simply clear the fault when ratelimited */
+ ratelimited = !__ratelimit(&rs);

raw_spin_lock_irqsave(&iommu->register_lock, flag);
fault_status = readl(iommu->reg + DMAR_FSTS_REG);
- if (fault_status)
+ if (fault_status && !ratelimited)
pr_err("DRHD: handling fault status reg %x\n", fault_status);

/* TBD: ignore advanced fault log currently */
@@ -1507,24 +1514,28 @@ irqreturn_t dmar_fault(int irq, void *de
if (!(data & DMA_FRCD_F))
break;

- fault_reason = dma_frcd_fault_reason(data);
- type = dma_frcd_type(data);
-
- data = readl(iommu->reg + reg +
- fault_index * PRIMARY_FAULT_REG_LEN + 8);
- source_id = dma_frcd_source_id(data);
+ if (!ratelimited) {
+ fault_reason = dma_frcd_fault_reason(data);
+ type = dma_frcd_type(data);
+
+ data = readl(iommu->reg + reg +
+ fault_index * PRIMARY_FAULT_REG_LEN + 8);
+ source_id = dma_frcd_source_id(data);
+
+ guest_addr = dmar_readq(iommu->reg + reg +
+ fault_index * PRIMARY_FAULT_REG_LEN);
+ guest_addr = dma_frcd_page_addr(guest_addr);
+ }

- guest_addr = dmar_readq(iommu->reg + reg +
- fault_index * PRIMARY_FAULT_REG_LEN);
- guest_addr = dma_frcd_page_addr(guest_addr);
/* clear the fault */
writel(DMA_FRCD_F, iommu->reg + reg +
fault_index * PRIMARY_FAULT_REG_LEN + 12);

raw_spin_unlock_irqrestore(&iommu->register_lock, flag);

- dmar_fault_do_one(iommu, type, fault_reason,
- source_id, guest_addr);
+ if (!ratelimited)
+ dmar_fault_do_one(iommu, type, fault_reason,
+ source_id, guest_addr);

fault_index++;
if (fault_index >= cap_num_fault_regs(iommu->cap))