[PATCH RFC 2/2] xen: expose that grant table mappings update the IOMMU

[Roger Pau Monne <roger.pau@citrix.com>]

Add a new XENFEAT_hvm_gntmap_supports_iommu that is used to check
whether the hypervisor properly updates the IOMMU on auto-translated
guests when doing a grant table map/unmap operation.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Mukesh Rathor <mukesh.rathor@oracle.com>
Cc: Keir Fraser <keir@xen.org>
Cc: Jan Beulich <jbeulich@suse.com>
---
 xen/common/kernel.c           |    2 ++
 xen/include/public/features.h |    6 ++++++
 2 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/xen/common/kernel.c b/xen/common/kernel.c
index b371f8f..7589dc1 100644
--- a/xen/common/kernel.c
+++ b/xen/common/kernel.c
@@ -316,11 +316,13 @@ DO(xen_version)(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
             case guest_type_pvh:
                 fi.submap |= (1U << XENFEAT_hvm_safe_pvclock) |
                              (1U << XENFEAT_supervisor_mode_kernel) |
+                             (1U << XENFEAT_hvm_gntmap_supports_iommu) |
                              (1U << XENFEAT_hvm_callback_vector);
                 break;
             case guest_type_hvm:
                 fi.submap |= (1U << XENFEAT_hvm_safe_pvclock) |
                              (1U << XENFEAT_hvm_callback_vector) |
+                             (1U << XENFEAT_hvm_gntmap_supports_iommu) |
                              (1U << XENFEAT_hvm_pirqs);
                 break;
             }
diff --git a/xen/include/public/features.h b/xen/include/public/features.h
index a149aa6..eaa0187 100644
--- a/xen/include/public/features.h
+++ b/xen/include/public/features.h
@@ -94,6 +94,12 @@
 /* operation as Dom0 is supported */
 #define XENFEAT_dom0                      11
 
+/*
+ * If set, GNTTABOP_map_grant_ref sets the proper IOMMU mappings so the
+ * resulting mapped page can be used for IO with hardware devices.
+ */
+#define XENFEAT_hvm_gntmap_supports_iommu 12
+
 #define XENFEAT_NR_SUBMAPS 1
 
 #endif /* __XEN_PUBLIC_FEATURES_H__ */
-- 
1.7.7.5 (Apple Git-26)


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