[ 01/82] iommu/amd: Add workaround for event log erratum

Ben Hutchings
2012-06-08T05:06:47Z

From: Joerg Roedel <joerg.roedel@amd.com>

commit 3d06fca8d2aa3543030e40b95f1d62f9f5a03540 upstream.

Due to a recent erratum it can happen that the head pointer
of the event-log is updated before the actual event-log
entry is written. This patch implements the recommended
workaround.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/iommu/amd_iommu.c | 29 +++++++++++++++++++++++------
1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 08f3eec..d90a421 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -450,12 +450,27 @@ static void dump_command(unsigned long phys_addr)

static void iommu_print_event(struct amd_iommu *iommu, void *__evt)
{
- u32 *event = __evt;
- int type = (event[1] >> EVENT_TYPE_SHIFT) & EVENT_TYPE_MASK;
- int devid = (event[0] >> EVENT_DEVID_SHIFT) & EVENT_DEVID_MASK;
- int domid = (event[1] >> EVENT_DOMID_SHIFT) & EVENT_DOMID_MASK;
- int flags = (event[1] >> EVENT_FLAGS_SHIFT) & EVENT_FLAGS_MASK;
- u64 address = (u64)(((u64)event[3]) << 32) | event[2];
+ int type, devid, domid, flags;
+ volatile u32 *event = __evt;
+ int count = 0;
+ u64 address;
+
+retry:
+ type = (event[1] >> EVENT_TYPE_SHIFT) & EVENT_TYPE_MASK;
+ devid = (event[0] >> EVENT_DEVID_SHIFT) & EVENT_DEVID_MASK;
+ domid = (event[1] >> EVENT_DOMID_SHIFT) & EVENT_DOMID_MASK;
+ flags = (event[1] >> EVENT_FLAGS_SHIFT) & EVENT_FLAGS_MASK;
+ address = (u64)(((u64)event[3]) << 32) | event[2];
+
+ if (type == 0) {
+ /* Did we hit the erratum? */
+ if (++count == LOOP_TIMEOUT) {
+ pr_err("AMD-Vi: No event written to event log\n");
+ return;
+ }
+ udelay(1);
+ goto retry;
+ }

printk(KERN_ERR "AMD-Vi: Event logged [");

@@ -508,6 +523,8 @@ static void iommu_print_event(struct amd_iommu *iommu, void *__evt)
default:
printk(KERN_ERR "UNKNOWN type=0x%02x]\n", type);
}
+
+ memset(__evt, 0, 4 * sizeof(u32));
}

static void iommu_poll_events(struct amd_iommu *iommu)