[Xen-changelog] [xen master] iommu: add iommu_intpost to control VT-d Posted-Interrupts feature

[patchbot@xxxxxxx]

commit 9670e7df84180748fbd2bb74162a1e557d75df75
Author:     Feng Wu <feng.wu@xxxxxxxxx>
AuthorDate: Tue Nov 24 12:09:28 2015 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Nov 24 12:09:28 2015 +0100

    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@xxxxxxxxx>
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
    Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/drivers/passthrough/iommu.c |   13 ++++++++++++-
 xen/include/xen/iommu.h         |    2 +-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 3e55abf..3d02550 100644
--- 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 8f3a20e..1f5d04a 100644
--- 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;
--
generated by git-patchbot for /home/xen/git/xen.git#master

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