[PATCH v10 1/3] vt-d: add a timeout parameter for Queued Invalidation

[Quan Xu <quan.xu@intel.com>]

The parameter 'vtd_qi_timeout' specifies the timeout of the
VT-d Queued Invalidation in milliseconds. By default, the
timeout is 1ms, which can be boot-time changed.

Add a __must_check annotation. The followup patch titled
'VT-d IOTLB/Context/IEC flush issue' addresses the __mustcheck.
That is the other callers of this routine (two or three levels up)
ignore the return code. This patch does not address this but the
other does.

Signed-off-by: Quan Xu <quan.xu@intel.com>
---
 docs/misc/xen-command-line.markdown  | 10 ++++++++++
 xen/drivers/passthrough/vtd/qinval.c | 17 ++++++++++++-----
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index ca77e3b..0b83068 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -1532,6 +1532,16 @@ Note that if **watchdog** option is also specified vpmu will be turned off.
 As the virtualisation is not 100% safe, don't use the vpmu flag on
 production systems (see http://xenbits.xen.org/xsa/advisory-163.html)!
 
+### vtd\_qi\_timeout (VT-d)
+> `= <integer>`
+
+> Default: `1`
+
+Specify the timeout of the VT-d Queued Invalidation in milliseconds.
+
+By default, the timeout is 1ms. When you see error 'Queue invalidate wait
+descriptor timed out', try increasing this value.
+
 ### watchdog
 > `= force | <boolean>`
 
diff --git a/xen/drivers/passthrough/vtd/qinval.c b/xen/drivers/passthrough/vtd/qinval.c
index b81b0bd..52ba2c2 100644
--- a/xen/drivers/passthrough/vtd/qinval.c
+++ b/xen/drivers/passthrough/vtd/qinval.c
@@ -28,6 +28,11 @@
 #include "vtd.h"
 #include "extern.h"
 
+static unsigned int __read_mostly vtd_qi_timeout = 1;
+integer_param("vtd_qi_timeout", vtd_qi_timeout);
+
+#define IOMMU_QI_TIMEOUT (vtd_qi_timeout * MILLISECS(1))
+
 static void print_qi_regs(struct iommu *iommu)
 {
     u64 val;
@@ -130,10 +135,10 @@ static void queue_invalidate_iotlb(struct iommu *iommu,
     spin_unlock_irqrestore(&iommu->register_lock, flags);
 }
 
-static int queue_invalidate_wait(struct iommu *iommu,
+static int __must_check queue_invalidate_wait(struct iommu *iommu,
     u8 iflag, u8 sw, u8 fn)
 {
-    s_time_t start_time;
+    s_time_t timeout;
     volatile u32 poll_slot = QINVAL_STAT_INIT;
     unsigned int index;
     unsigned long flags;
@@ -164,13 +169,15 @@ static int queue_invalidate_wait(struct iommu *iommu,
     if ( sw )
     {
         /* In case all wait descriptor writes to same addr with same data */
-        start_time = NOW();
+        timeout = NOW() + IOMMU_QI_TIMEOUT;
         while ( poll_slot != QINVAL_STAT_DONE )
         {
-            if ( NOW() > (start_time + DMAR_OPERATION_TIMEOUT) )
+            if ( NOW() > timeout )
             {
                 print_qi_regs(iommu);
-                panic("queue invalidate wait descriptor was not executed");
+                printk(XENLOG_WARNING VTDPREFIX
+                       "Queue invalidate wait descriptor timed out.\n");
+                return -ETIMEDOUT;
             }
             cpu_relax();
         }
-- 
1.9.1


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