[PATCH RFC 23/31] xen/x86: Export cpuid levelling capabilities via SYSCTL

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

This allows the toolstack to query what exactly Xen can control in a PV guest
issuing a native `cpuid` instruction.

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/cpu/common.c       |  3 +++
 xen/arch/x86/sysctl.c           |  6 ++++++
 xen/include/asm-x86/processor.h | 13 +++++++++++++
 xen/include/public/sysctl.h     | 30 ++++++++++++++++++++++++++++++
 4 files changed, 52 insertions(+)

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 7b89ebd..2ad85e0 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -32,6 +32,9 @@ integer_param("cpuid_mask_ext_ecx", opt_cpuid_mask_ext_ecx);
 unsigned int __devinitdata opt_cpuid_mask_ext_edx = ~0u;
 integer_param("cpuid_mask_ext_edx", opt_cpuid_mask_ext_edx);
 
+unsigned int __initdata expected_levelling_cap;
+unsigned int __read_mostly levelling_caps;
+
 const struct cpu_dev *__read_mostly cpu_devs[X86_VENDOR_NUM] = {};
 
 unsigned int paddr_bits __read_mostly = 36;
diff --git a/xen/arch/x86/sysctl.c b/xen/arch/x86/sysctl.c
index 50b2fd4..b01c968 100644
--- a/xen/arch/x86/sysctl.c
+++ b/xen/arch/x86/sysctl.c
@@ -253,6 +253,12 @@ long arch_do_sysctl(
         break;
     }
 
+    case XEN_SYSCTL_get_levelling_caps:
+        sysctl->u.levelling.caps = levelling_caps;
+        if ( __copy_to_guest(u_sysctl, sysctl, 1) )
+            ret = -EFAULT;
+        break;
+
     default:
         ret = -ENOSYS;
         break;
diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index f507f5e..b2c3653 100644
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -572,6 +572,19 @@ void microcode_set_module(unsigned int);
 int microcode_update(XEN_GUEST_HANDLE_PARAM(const_void), unsigned long len);
 int microcode_resume_cpu(unsigned int cpu);
 
+#define LCAP_faulting XEN_SYSCTL_LEVELCAP_faulting
+#define LCAP_1cd      (XEN_SYSCTL_LEVELCAP_1c  | XEN_SYSCTL_LEVELCAP_1d)
+#define LCAP_e1cd     (XEN_SYSCTL_LEVELCAP_e1c | XEN_SYSCTL_LEVELCAP_e1d)
+#define LCAP_Da1      XEN_SYSCTL_LEVELCAP_Da1
+#define LCAP_6c       XEN_SYSCTL_LEVELCAP_6c
+#define LCAP_7ab0     (XEN_SYSCTL_LEVELCAP_7a0 | XEN_SYSCTL_LEVELCAP_7b0)
+
+/*
+ * Expected levelling capabilities (given cpuid vendor/family information),
+ * and levelling capabilities actually available (given MSR probing).
+ */
+extern unsigned int expected_levelling_cap, levelling_caps;
+
 enum get_cpu_vendor {
    gcv_host_early,
    gcv_host_late,
diff --git a/xen/include/public/sysctl.h b/xen/include/public/sysctl.h
index 3119b7b..7b134c6 100644
--- a/xen/include/public/sysctl.h
+++ b/xen/include/public/sysctl.h
@@ -785,6 +785,34 @@ struct xen_sysctl_featureset {
 typedef struct xen_sysctl_featureset xen_sysctl_featureset_t;
 DEFINE_XEN_GUEST_HANDLE(xen_sysctl_featureset_t);
 
+/*
+ * XEN_SYSCTL_get_levelling_caps (x86 specific)
+ *
+ * Return hardware capabilities concerning masking or faulting of the cpuid
+ * instruction for PV guests.
+ */
+struct xen_sysctl_levelling_caps {
+/*
+ * Featureset array index encoding:
+ * - (possibly) 'e' Extended
+ * - leaf, uppercase hex
+ * - register, lowercase
+ * - (possibly) subleaf
+ */
+#define XEN_SYSCTL_LEVELCAP_faulting (1ul <<  0) /* CPUID faulting    */
+#define XEN_SYSCTL_LEVELCAP_1c       (1ul <<  1) /* 0x00000001.ecx    */
+#define XEN_SYSCTL_LEVELCAP_1d       (1ul <<  2) /* 0x00000001.edx    */
+#define XEN_SYSCTL_LEVELCAP_e1c      (1ul <<  3) /* 0x80000001.ecx    */
+#define XEN_SYSCTL_LEVELCAP_e1d      (1ul <<  4) /* 0x80000001.edx    */
+#define XEN_SYSCTL_LEVELCAP_Da1      (1ul <<  5) /* 0x0000000D:1.eax  */
+#define XEN_SYSCTL_LEVELCAP_6c       (1ul <<  6) /* 0x00000006.ecx    */
+#define XEN_SYSCTL_LEVELCAP_7a0      (1ul <<  7) /* 0x00000007:0.eax  */
+#define XEN_SYSCTL_LEVELCAP_7b0      (1ul <<  8) /* 0x00000007:0.ebx  */
+    uint64_t caps;
+};
+typedef struct xen_sysctl_levelling_caps xen_sysctl_levelling_caps_t;
+DEFINE_XEN_GUEST_HANDLE(xen_sysctl_levelling_caps_t);
+
 struct xen_sysctl {
     uint32_t cmd;
 #define XEN_SYSCTL_readconsole                    1
@@ -811,6 +839,7 @@ struct xen_sysctl {
 #define XEN_SYSCTL_psr_cat_op                    23
 #define XEN_SYSCTL_tmem_op                       24
 #define XEN_SYSCTL_get_featureset                25
+#define XEN_SYSCTL_get_levelling_caps            26
     uint32_t interface_version; /* XEN_SYSCTL_INTERFACE_VERSION */
     union {
         struct xen_sysctl_readconsole       readconsole;
@@ -837,6 +866,7 @@ struct xen_sysctl {
         struct xen_sysctl_psr_cat_op        psr_cat_op;
         struct xen_sysctl_tmem_op           tmem_op;
         struct xen_sysctl_featureset        featureset;
+        struct xen_sysctl_levelling_caps    levelling;
         uint8_t                             pad[128];
     } u;
 };
-- 
2.1.4