iommu: add iommu_intpost to control VT-d Posted-Interrupts feature

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>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 3e55abf63c1ecb8507dfa86c533eaac8af4b3e41..3d02550f731f059c96cf262bcf07977f5e2444a8 100644 (file)
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -57,6 +57,14 @@ 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;
+
+/*
+ * In the current implementation of VT-d posted interrupts, in some extreme
+ * cases, the per cpu list which saves the blocked vCPU will be very long,
+ * and this will affect the interrupt latency, so let this feature off by
+ * default until we find a good solution to resolve it.
+ */
+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;
@@ -307,6 +315,9 @@ 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;
@@ -374,7 +385,7 @@ 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;
 }
 
 int iommu_get_reserved_device_memory(iommu_grdm_t *func, void *ctxt)

diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index 8f3a20eb32e950b36265ac445214152aaed390aa..1f5d04a2430ba7d3b78493280ab0e950b541f772 100644 (file)
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -30,7 +30,7 @@
 extern bool_t iommu_enable, iommu_enabled;
 extern bool_t force_iommu, iommu_verbose;
 extern bool_t iommu_workaround_bios_bug, iommu_igfx, 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;