[PATCH RFC 07/31] xen/x86: Export host featureset via SYSCTL

[Andrew Cooper <andrew.cooper3@citrix.com>]

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Tim Deegan <tim@xen.org>
CC: Ian Campbell <Ian.Campbell@citrix.com>
---
 xen/arch/x86/sysctl.c       | 51 +++++++++++++++++++++++++++++++++++++++++++++
 xen/include/public/sysctl.h | 20 ++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/xen/arch/x86/sysctl.c b/xen/arch/x86/sysctl.c
index 38b5dcb..1f483b8 100644
--- a/xen/arch/x86/sysctl.c
+++ b/xen/arch/x86/sysctl.c
@@ -29,6 +29,7 @@
 #include <xen/cpu.h>
 #include <xsm/xsm.h>
 #include <asm/psr.h>
+#include <asm/cpuid.h>
 
 #define get_xen_guest_handle(val, hnd)  do { val = (hnd).p; } while (0)
 
@@ -190,6 +191,56 @@ long arch_do_sysctl(
         }
         break;
 
+    case XEN_SYSCTL_get_featureset:
+    {
+        uint32_t *featureset;
+        unsigned int nr;
+
+        /* Request for maximum number of features? */
+        if ( guest_handle_is_null(sysctl->u.featureset.features) )
+        {
+            sysctl->u.featureset.nr_features = XEN_NR_FEATURESET_ENTRIES;
+            if ( __copy_to_guest(u_sysctl, sysctl, 1) )
+                ret = -EFAULT;
+            break;
+        }
+
+        /* Clip the number of entries. */
+        nr = min_t(unsigned int, sysctl->u.featureset.nr_features,
+                   XEN_NR_FEATURESET_ENTRIES);
+
+        switch ( sysctl->u.featureset.index )
+        {
+        case XEN_SYSCTL_featureset_host:
+            featureset = host_featureset;
+            break;
+
+        default:
+            featureset = NULL;
+            break;
+        }
+
+        /* Bad featureset index? */
+        if ( !ret && !featureset )
+            ret = -EINVAL;
+
+        /* Copy the requested featureset into place. */
+        if ( !ret && copy_to_guest(sysctl->u.featureset.features,
+                                   featureset, nr) )
+            ret = -EFAULT;
+
+        /* Inform the caller of how many features we wrote. */
+        sysctl->u.featureset.nr_features = nr;
+        if ( !ret && __copy_to_guest(u_sysctl, sysctl, 1) )
+            ret = -EFAULT;
+
+        /* Inform the caller if there was more data to provide. */
+        if ( !ret && nr < XEN_NR_FEATURESET_ENTRIES )
+            ret = -ENOBUFS;
+
+        break;
+    }
+
     default:
         ret = -ENOSYS;
         break;
diff --git a/xen/include/public/sysctl.h b/xen/include/public/sysctl.h
index 0cacacc..dfde433 100644
--- a/xen/include/public/sysctl.h
+++ b/xen/include/public/sysctl.h
@@ -764,6 +764,24 @@ struct xen_sysctl_tmem_op {
 typedef struct xen_sysctl_tmem_op xen_sysctl_tmem_op_t;
 DEFINE_XEN_GUEST_HANDLE(xen_sysctl_tmem_op_t);
 
+/*
+ * XEN_SYSCTL_get_featureset (x86 specific)
+ *
+ * Return information about the maximum sets of features which can be offered
+ * to different types of guests.  This is all strictly information as found in
+ * `cpuid` feature leaves with no synthetic alterations.
+ */
+struct xen_sysctl_featureset {
+#define XEN_SYSCTL_featureset_host      0
+    uint32_t index;       /* IN: Which featureset to query? */
+    uint32_t nr_features; /* IN/OUT: Number of entries in/written to
+                           * 'features', or the maximum number of features if
+                           * the guest handle is NULL. */
+    XEN_GUEST_HANDLE_64(uint32) features; /* OUT: */
+};
+typedef struct xen_sysctl_featureset xen_sysctl_featureset_t;
+DEFINE_XEN_GUEST_HANDLE(xen_sysctl_featureset_t);
+
 struct xen_sysctl {
     uint32_t cmd;
 #define XEN_SYSCTL_readconsole                    1
@@ -789,6 +807,7 @@ struct xen_sysctl {
 #define XEN_SYSCTL_pcitopoinfo                   22
 #define XEN_SYSCTL_psr_cat_op                    23
 #define XEN_SYSCTL_tmem_op                       24
+#define XEN_SYSCTL_get_featureset                25
     uint32_t interface_version; /* XEN_SYSCTL_INTERFACE_VERSION */
     union {
         struct xen_sysctl_readconsole       readconsole;
@@ -814,6 +833,7 @@ struct xen_sysctl {
         struct xen_sysctl_psr_cmt_op        psr_cmt_op;
         struct xen_sysctl_psr_cat_op        psr_cat_op;
         struct xen_sysctl_tmem_op           tmem_op;
+        struct xen_sysctl_featureset        featureset;
         uint8_t                             pad[128];
     } u;
 };
-- 
2.1.4