[RFC v1 02/15] vt-d: VT-d Posted-Interrupts feature detection

[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 feature detection logic for VT-d posted-interrupt.

Signed-off-by: Feng Wu <feng.wu@intel.com>
---
 xen/drivers/passthrough/vtd/iommu.c | 15 +++++++++++++--
 xen/drivers/passthrough/vtd/iommu.h |  1 +
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
index 891b9e3..86798a3 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -2030,6 +2030,7 @@ static int init_vtd_hw(void)
             if ( ioapic_to_iommu(IO_APIC_ID(apic)) == NULL )
             {
                 iommu_intremap = 0;
+                iommu_intpost = 0;
                 dprintk(XENLOG_ERR VTDPREFIX,
                     "ioapic_to_iommu: ioapic %#x (id: %#x) is NULL! "
                     "Will not try to enable Interrupt Remapping.\n",
@@ -2046,6 +2047,7 @@ static int init_vtd_hw(void)
             if ( enable_intremap(iommu, 0) != 0 )
             {
                 iommu_intremap = 0;
+                iommu_intpost = 0;
                 dprintk(XENLOG_WARNING VTDPREFIX,
                         "Interrupt Remapping not enabled\n");
 
@@ -2119,8 +2121,8 @@ int __init intel_vtd_setup(void)
     }
 
     /* We enable the following features only if they are supported by all VT-d
-     * engines: Snoop Control, DMA passthrough, Queued Invalidation and
-     * Interrupt Remapping.
+     * engines: Snoop Control, DMA passthrough, Queued Invalidation, Interrupt
+     * Remapping, and Posted Interrupt
      */
     for_each_drhd_unit ( drhd )
     {
@@ -2146,7 +2148,13 @@ int __init intel_vtd_setup(void)
             iommu_qinval = 0;
 
         if ( iommu_intremap && !ecap_intr_remap(iommu->ecap) )
+        {
             iommu_intremap = 0;
+            iommu_intpost = 0;
+        }
+
+        if ( iommu_intpost && !cap_intr_post(iommu->cap))
+            iommu_intpost = 0;
 
         if ( !vtd_ept_page_compatible(iommu) )
             iommu_hap_pt_share = 0;
@@ -2164,6 +2172,7 @@ int __init intel_vtd_setup(void)
     if ( !iommu_qinval && iommu_intremap )
     {
         iommu_intremap = 0;
+        iommu_intpost = 0;
         dprintk(XENLOG_WARNING VTDPREFIX, "Interrupt Remapping disabled "
             "since Queued Invalidation isn't supported or enabled.\n");
     }
@@ -2173,6 +2182,7 @@ int __init intel_vtd_setup(void)
     P(iommu_passthrough, "Dom0 DMA Passthrough");
     P(iommu_qinval, "Queued Invalidation");
     P(iommu_intremap, "Interrupt Remapping");
+    P(iommu_intpost, "Posted Interrupt");
     P(iommu_hap_pt_share, "Shared EPT tables");
 #undef P
 
@@ -2192,6 +2202,7 @@ int __init intel_vtd_setup(void)
     iommu_passthrough = 0;
     iommu_qinval = 0;
     iommu_intremap = 0;
+    iommu_intpost = 0;
     return ret;
 }
 
diff --git a/xen/drivers/passthrough/vtd/iommu.h b/xen/drivers/passthrough/vtd/iommu.h
index d6e6520..42047e0 100644
--- a/xen/drivers/passthrough/vtd/iommu.h
+++ b/xen/drivers/passthrough/vtd/iommu.h
@@ -69,6 +69,7 @@
 /*
  * Decoding Capability Register
  */
+#define cap_intr_post(c)       (((c) >> 59) & 1)
 #define cap_read_drain(c)      (((c) >> 55) & 1)
 #define cap_write_drain(c)     (((c) >> 54) & 1)
 #define cap_max_amask_val(c)   (((c) >> 48) & 0x3f)
-- 
2.1.0