[v3 04/15] iommu: Add iommu_intpost to control VT-d Posted-Interrupts feature

[Feng Wu <feng.wu@intel.com>]

VT-d Posted-Interrupts is an enhancement to CPU side Posted-Interrupt.
With VT-d Posted-Interrupts enabled, external interrupts from
direct-assigned devices can be delivered to guests without VMM
intervention when guest is running in non-root mode.

This patch adds variable 'iommu_intpost' to control whether enable VT-d
posted-interrupt or not in the generic IOMMU code.

Signed-off-by: Feng Wu <feng.wu@intel.com>
---
v3:
- Remove pointless initializer for 'iommu_intpost'.
- Some adjustment for "if no intremap then no intpost" logic.
    * For parse_iommu_param(), move it to the end of the function,
      so we don't need to add the some logic when introduing the
      new kernel parameter 'intpost' in later patch.
    * Add this logic in iommu_setup() after iommu_hardware_setup()
      is called.

 xen/drivers/passthrough/iommu.c | 10 +++++++++-
 xen/include/xen/iommu.h         |  2 +-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 06cb38f..597f676 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -39,6 +39,7 @@ static void iommu_dump_p2m_table(unsigned char key);
  *   no-snoop                   Disable VT-d Snoop Control
  *   no-qinval                  Disable VT-d Queued Invalidation
  *   no-intremap                Disable VT-d Interrupt Remapping
+ *   no-intpost                 Disable VT-d Interrupt posting
  */
 custom_param("iommu", parse_iommu_param);
 bool_t __initdata iommu_enable = 1;
@@ -51,6 +52,7 @@ bool_t __read_mostly iommu_passthrough;
 bool_t __read_mostly iommu_snoop = 1;
 bool_t __read_mostly iommu_qinval = 1;
 bool_t __read_mostly iommu_intremap = 1;
+bool_t __read_mostly iommu_intpost;
 bool_t __read_mostly iommu_hap_pt_share = 1;
 bool_t __read_mostly iommu_debug;
 bool_t __read_mostly amd_iommu_perdev_intremap = 1;
@@ -112,6 +114,9 @@ static void __init parse_iommu_param(char *s)
 
         s = ss + 1;
     } while ( ss );
+
+    if ( !iommu_intremap )
+        iommu_intpost = 0;
 }
 
 int iommu_domain_init(struct domain *d)
@@ -305,6 +310,9 @@ int __init iommu_setup(void)
         panic("Couldn't enable %s and iommu=required/force",
               !iommu_enabled ? "IOMMU" : "Interrupt Remapping");
 
+    if ( !iommu_intremap )
+        iommu_intpost = 0;
+
     if ( !iommu_enabled )
     {
         iommu_snoop = 0;
@@ -372,7 +380,7 @@ void iommu_crash_shutdown(void)
     const struct iommu_ops *ops = iommu_get_ops();
     if ( iommu_enabled )
         ops->crash_shutdown();
-    iommu_enabled = iommu_intremap = 0;
+    iommu_enabled = iommu_intremap = iommu_intpost = 0;
 }
 
 bool_t iommu_has_feature(struct domain *d, enum iommu_feature feature)
diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index b30bf41..a123cce 100644
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -31,7 +31,7 @@
 extern bool_t iommu_enable, iommu_enabled;
 extern bool_t force_iommu, iommu_verbose;
 extern bool_t iommu_workaround_bios_bug, iommu_passthrough;
-extern bool_t iommu_snoop, iommu_qinval, iommu_intremap;
+extern bool_t iommu_snoop, iommu_qinval, iommu_intremap, iommu_intpost;
 extern bool_t iommu_hap_pt_share;
 extern bool_t iommu_debug;
 extern bool_t amd_iommu_perdev_intremap;
-- 
2.1.0