[Patch v11 1/3] IOMMU: add a timeout parameter for device IOTLB invalidation

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

From: Quan Xu <quan.xu@intel.com>

The parameter 'iommu_dev_iotlb_timeout' specifies the timeout of
the device IOTLB 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.

v11: Change the timeout parameter from 'vtd_qi_timeout' to
    'iommu_dev_iotlb_timeout', which is not only for VT-d device
    IOTLB invalidation, but also for other IOMMU implementations.

Signed-off-by: Quan Xu <quan.xu@intel.com>
---
 docs/misc/xen-command-line.markdown  |  9 +++++++++
 xen/drivers/passthrough/iommu.c      |  3 +++
 xen/drivers/passthrough/vtd/qinval.c | 34 +++++++++++++++++++++++-----------
 xen/include/xen/iommu.h              |  2 ++
 4 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index b4bae11..34a0f9c 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -996,6 +996,15 @@ debug hypervisor only).
 
 >> Enable IOMMU debugging code (implies `verbose`).
 
+### iommu\_dev\_iotlb\_timeout
+> `= <integer>`
+
+> Default: `1`
+
+Specify the timeout of the device IOTLB invalidation in milliseconds.
+By default, the timeout is 1 ms. When you see error 'Queue invalidate
+wait descriptor timed out', try increasing this value.
+
 ### iommu\_inclusive\_mapping (VT-d)
 > `= <boolean>`
 
diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 098b601..e12de69 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -24,6 +24,9 @@
 static void parse_iommu_param(char *s);
 static void iommu_dump_p2m_table(unsigned char key);
 
+unsigned int __read_mostly iommu_dev_iotlb_timeout = 1;
+integer_param("iommu_dev_iotlb_timeout", iommu_dev_iotlb_timeout);
+
 /*
  * The 'iommu' parameter enables the IOMMU.  Optional comma separated
  * value may contain:
diff --git a/xen/drivers/passthrough/vtd/qinval.c b/xen/drivers/passthrough/vtd/qinval.c
index aa7841a..1a37565 100644
--- a/xen/drivers/passthrough/vtd/qinval.c
+++ b/xen/drivers/passthrough/vtd/qinval.c
@@ -28,6 +28,8 @@
 #include "vtd.h"
 #include "extern.h"
 
+#define IOMMU_QI_TIMEOUT MILLISECS(1)
+
 static void print_qi_regs(struct iommu *iommu)
 {
     u64 val;
@@ -130,10 +132,10 @@ static void queue_invalidate_iotlb(struct iommu *iommu,
     spin_unlock_irqrestore(&iommu->register_lock, flags);
 }
 
-static int queue_invalidate_wait(struct iommu *iommu,
-    u8 iflag, u8 sw, u8 fn)
+static int __must_check queue_invalidate_wait(struct iommu *iommu,
+                                              u8 iflag, u8 sw, u8 fn,
+                                              bool_t flush_dev_iotlb)
 {
-    s_time_t start_time;
     volatile u32 poll_slot = QINVAL_STAT_INIT;
     unsigned int index;
     unsigned long flags;
@@ -163,14 +165,21 @@ static int queue_invalidate_wait(struct iommu *iommu,
     /* Now we don't support interrupt method */
     if ( sw )
     {
+        s_time_t timeout;
+
         /* In case all wait descriptor writes to same addr with same data */
-        start_time = NOW();
+        timeout = flush_dev_iotlb ?
+                  (NOW() + iommu_dev_iotlb_timeout * MILLISECS(1)) :
+                  (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();
         }
@@ -180,12 +189,14 @@ static int queue_invalidate_wait(struct iommu *iommu,
     return -EOPNOTSUPP;
 }
 
-static int invalidate_sync(struct iommu *iommu)
+static int __must_check invalidate_sync(struct iommu *iommu,
+                                        bool_t flush_dev_iotlb)
 {
     struct qi_ctrl *qi_ctrl = iommu_qi_ctrl(iommu);
 
     if ( qi_ctrl->qinval_maddr )
-        return queue_invalidate_wait(iommu, 0, 1, 1);
+        return queue_invalidate_wait(iommu, 0, 1, 1, flush_dev_iotlb);
+
     return 0;
 }
 
@@ -254,7 +265,7 @@ static int __iommu_flush_iec(struct iommu *iommu, u8 granu, u8 im, u16 iidx)
     int ret;
 
     queue_invalidate_iec(iommu, granu, im, iidx);
-    ret = invalidate_sync(iommu);
+    ret = invalidate_sync(iommu, 0);
     /*
      * reading vt-d architecture register will ensure
      * draining happens in implementation independent way.
@@ -300,7 +311,7 @@ static int __must_check flush_context_qi(void *_iommu, u16 did,
     {
         queue_invalidate_context(iommu, did, sid, fm,
                                  type >> DMA_CCMD_INVL_GRANU_OFFSET);
-        ret = invalidate_sync(iommu);
+        ret = invalidate_sync(iommu, 0);
     }
     return ret;
 }
@@ -344,10 +355,11 @@ static int __must_check flush_iotlb_qi(void *_iommu, u16 did, u64 addr,
                                dw, did, size_order, 0, addr);
         if ( flush_dev_iotlb )
             ret = dev_invalidate_iotlb(iommu, did, addr, size_order, type);
-        rc = invalidate_sync(iommu);
+        rc = invalidate_sync(iommu, flush_dev_iotlb);
         if ( !ret )
             ret = rc;
     }
+
     return ret;
 }
 
diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index e917031..9891bc5 100644
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -35,6 +35,8 @@ extern bool_t iommu_hap_pt_share;
 extern bool_t iommu_debug;
 extern bool_t amd_iommu_perdev_intremap;
 
+extern unsigned int iommu_dev_iotlb_timeout;
+
 #define IOMMU_PAGE_SIZE(sz) (1UL << PAGE_SHIFT_##sz)
 #define IOMMU_PAGE_MASK(sz) (~(u64)0 << PAGE_SHIFT_##sz)
 #define IOMMU_PAGE_ALIGN(sz, addr)  (((addr) + ~PAGE_MASK_##sz) & PAGE_MASK_##sz)
-- 
1.9.1


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