iommu/vt-d: Ratelimit fault handler

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>

diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index 8ffd756..8f8bfff 100644 (file)
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -1602,10 +1602,17 @@ irqreturn_t dmar_fault(int irq, void *dev_id)
        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 */
@@ -1627,24 +1634,28 @@ irqreturn_t dmar_fault(int irq, void *dev_id)
                if (!(data & DMA_FRCD_F))
                        break;
 
-               fault_reason = dma_frcd_fault_reason(data);
-               type = dma_frcd_type(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);
+                       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))