[Xen-devel] [PATCH] public/sysctl: Clarifications to XEN_SYSCTL_PHYSCAP_hvm_directio

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Specifically that it indicates passthrough support for PV guests as well

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Keir Fraser <keir@xxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
---
 xen/include/public/sysctl.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/xen/include/public/sysctl.h b/xen/include/public/sysctl.h
index 96680eb..cbbeecd 100644
--- a/xen/include/public/sysctl.h
+++ b/xen/include/public/sysctl.h
@@ -89,7 +89,14 @@ DEFINE_XEN_GUEST_HANDLE(xen_sysctl_tbuf_op_t);
  /* (x86) The platform supports HVM guests. */
 #define _XEN_SYSCTL_PHYSCAP_hvm          0
 #define XEN_SYSCTL_PHYSCAP_hvm           (1u<<_XEN_SYSCTL_PHYSCAP_hvm)
- /* (x86) The platform supports HVM-guest direct access to I/O devices. */
+ /*
+  * (x86) The platform supports guest direct access to I/O devices.
+  *
+  * Note that this parameter has been misnamed since its introduction, and is
+  * now too baked into APIs and ABIs to change.  Despite the "hvm" in its
+  * name, it simply indicates the presence of an enabled IOMMU, allowing for
+  * passthrough of devices to guests, including PV guests.
+  */
 #define _XEN_SYSCTL_PHYSCAP_hvm_directio 1
 #define XEN_SYSCTL_PHYSCAP_hvm_directio  (1u<<_XEN_SYSCTL_PHYSCAP_hvm_directio)
 struct xen_sysctl_physinfo {
-- 
2.1.4


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel