iommu/amd: Workaround for erratum 787

The IOMMU interrupt handling in bottom half must clear the PPR log interrupt
and event log interrupt bits to re-enable the interrupt. This is done by
writing 1 to the memory mapped register to clear the bit. Due to hardware bug,
if the driver tries to clear this bit while the IOMMU hardware also setting
this bit, the conflict will result with the bit being set. If the interrupt
handling code does not make sure to clear this bit, subsequent changes in the
event/PPR logs will no longer generating interrupts, and would result if
buffer overflow. After clearing the bits, the driver must read back
the register to verify.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Adjust to apply on top of heavily modified patch 1. Adjust flow to get away
with a single readl() in each instance of the status register checks.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Tim Deegan <tim@xen.org>
Acked-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
master commit: 9eabb0735400e2b6059dfa3f0b47a426f61f570a
master date: 2013-07-02 08:50:41 +0200

diff --git a/xen/drivers/passthrough/amd/iommu_init.c b/xen/drivers/passthrough/amd/iommu_init.c
index b01e630ef31b4d483ac48f0cd6ba15146c503f00..ba86e1b3cf644a80a504235b3bcf033cde8b0d37 100644 (file)
--- a/xen/drivers/passthrough/amd/iommu_init.c
+++ b/xen/drivers/passthrough/amd/iommu_init.c
@@ -636,6 +636,14 @@ static void iommu_check_event_log(struct amd_iommu *iommu)
         }
     }
 
+    /*
+     * Workaround for erratum787:
+     * Re-check to make sure the bit has been cleared.
+     */
+    entry = readl(iommu->mmio_base + IOMMU_STATUS_MMIO_OFFSET);
+    if ( entry & IOMMU_STATUS_EVENT_LOG_INT_MASK )
+        tasklet_schedule(&amd_iommu_irq_tasklet);
+
     spin_unlock_irqrestore(&iommu->lock, flags);
 }
 
@@ -717,6 +725,14 @@ static void iommu_check_ppr_log(struct amd_iommu *iommu)
         }
     }
 
+    /*
+     * Workaround for erratum787:
+     * Re-check to make sure the bit has been cleared.
+     */
+    entry = readl(iommu->mmio_base + IOMMU_STATUS_MMIO_OFFSET);
+    if ( entry & IOMMU_STATUS_PPR_LOG_INT_MASK )
+        tasklet_schedule(&amd_iommu_irq_tasklet);
+
     spin_unlock_irqrestore(&iommu->lock, flags);
 }