[PATCH v4 13/26] x86/cpu: Sysctl and common infrastructure for levelling context switching

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

A toolstack needs to know how much control Xen has over the visible cpuid
values in PV guests.  Provide an explicit mechanism to query what Xen is
capable of.

This interface will currently report no capabilities.  This change is
scaffolding for future patches, which will introduce detection and switching
logic, after which the interface will report hardware capabilities correctly.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>

v2:
 * s/cpumasks/cpuidmasks/
v3:
 * Reintroduce XEN_SYSCTL_get_levelling_caps (requested by Joao for some
   development he has planned).
 * Rename to XEN_SYSCTL_get_cpu_levelling_caps, and rename the constants to
   match the Xen command line options.
v4:
 * Move declarations from processor.h to cpuid.h
 * API corrections for XEN_SYSCTL_get_levelling_caps
---
 xen/arch/x86/cpu/common.c        |  6 ++++++
 xen/arch/x86/sysctl.c            |  6 ++++++
 xen/include/asm-x86/cpufeature.h |  1 +
 xen/include/asm-x86/cpuid.h      | 32 ++++++++++++++++++++++++++++++++
 xen/include/public/sysctl.h      | 23 +++++++++++++++++++++++
 5 files changed, 68 insertions(+)

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index b5c023f..7ef75b0 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -36,6 +36,12 @@ integer_param("cpuid_mask_ext_ecx", opt_cpuid_mask_ext_ecx);
 unsigned int 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;
+
+DEFINE_PER_CPU(struct cpuidmasks, cpuidmasks);
+struct cpuidmasks __read_mostly cpuidmask_defaults;
+
 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 58cbd70..f68cbec 100644
--- a/xen/arch/x86/sysctl.c
+++ b/xen/arch/x86/sysctl.c
@@ -190,6 +190,12 @@ long arch_do_sysctl(
         }
         break;
 
+    case XEN_SYSCTL_get_cpu_levelling_caps:
+        sysctl->u.cpu_levelling_caps.caps = levelling_caps;
+        if ( __copy_field_to_guest(u_sysctl, sysctl, u.cpu_levelling_caps.caps) )
+            ret = -EFAULT;
+        break;
+
     default:
         ret = -ENOSYS;
         break;
diff --git a/xen/include/asm-x86/cpufeature.h b/xen/include/asm-x86/cpufeature.h
index e29b024..84d3220 100644
--- a/xen/include/asm-x86/cpufeature.h
+++ b/xen/include/asm-x86/cpufeature.h
@@ -81,6 +81,7 @@
 #define cpu_has_xsavec		boot_cpu_has(X86_FEATURE_XSAVEC)
 #define cpu_has_xgetbv1		boot_cpu_has(X86_FEATURE_XGETBV1)
 #define cpu_has_xsaves		boot_cpu_has(X86_FEATURE_XSAVES)
+#define cpu_has_hypervisor	boot_cpu_has(X86_FEATURE_HYPERVISOR)
 
 enum _cache_type {
     CACHE_TYPE_NULL = 0,
diff --git a/xen/include/asm-x86/cpuid.h b/xen/include/asm-x86/cpuid.h
index 4725672..9a21c25 100644
--- a/xen/include/asm-x86/cpuid.h
+++ b/xen/include/asm-x86/cpuid.h
@@ -3,6 +3,7 @@
 
 #include <asm/cpufeatureset.h>
 #include <asm/cpuid-autogen.h>
+#include <asm/percpu.h>
 
 #define FSCAPINTS FEATURESET_NR_ENTRIES
 
@@ -18,6 +19,7 @@
 
 #ifndef __ASSEMBLY__
 #include <xen/types.h>
+#include <public/sysctl.h>
 
 extern const uint32_t known_features[FSCAPINTS];
 extern const uint32_t special_features[FSCAPINTS];
@@ -31,6 +33,36 @@ void calculate_featuresets(void);
 
 const uint32_t *lookup_deep_deps(uint32_t feature);
 
+/*
+ * Expected levelling capabilities (given cpuid vendor/family information),
+ * and levelling capabilities actually available (given MSR probing).
+ */
+#define LCAP_faulting XEN_SYSCTL_CPU_LEVELCAP_faulting
+#define LCAP_1cd      (XEN_SYSCTL_CPU_LEVELCAP_ecx |        \
+                       XEN_SYSCTL_CPU_LEVELCAP_edx)
+#define LCAP_e1cd     (XEN_SYSCTL_CPU_LEVELCAP_extd_ecx |   \
+                       XEN_SYSCTL_CPU_LEVELCAP_extd_edx)
+#define LCAP_Da1      XEN_SYSCTL_CPU_LEVELCAP_xsave_eax
+#define LCAP_6c       XEN_SYSCTL_CPU_LEVELCAP_thermal_ecx
+#define LCAP_7ab0     (XEN_SYSCTL_CPU_LEVELCAP_l7s0_eax |   \
+                       XEN_SYSCTL_CPU_LEVELCAP_l7s0_ebx)
+extern unsigned int expected_levelling_cap, levelling_caps;
+
+struct cpuidmasks
+{
+    uint64_t _1cd;
+    uint64_t e1cd;
+    uint64_t Da1;
+    uint64_t _6c;
+    uint64_t _7ab0;
+};
+
+/* Per CPU shadows of masking MSR values, for lazy context switching. */
+DECLARE_PER_CPU(struct cpuidmasks, cpuidmasks);
+
+/* Default masking MSR values, calculated at boot. */
+extern struct cpuidmasks cpuidmask_defaults;
+
 #endif /* __ASSEMBLY__ */
 #endif /* !__X86_CPUID_H__ */
 
diff --git a/xen/include/public/sysctl.h b/xen/include/public/sysctl.h
index 96680eb..1ab16db 100644
--- a/xen/include/public/sysctl.h
+++ b/xen/include/public/sysctl.h
@@ -766,6 +766,27 @@ 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_cpu_levelling_caps (x86 specific)
+ *
+ * Return hardware capabilities concerning masking or faulting of the cpuid
+ * instruction for PV guests.
+ */
+struct xen_sysctl_cpu_levelling_caps {
+#define XEN_SYSCTL_CPU_LEVELCAP_faulting    (1ul <<  0) /* CPUID faulting    */
+#define XEN_SYSCTL_CPU_LEVELCAP_ecx         (1ul <<  1) /* 0x00000001.ecx    */
+#define XEN_SYSCTL_CPU_LEVELCAP_edx         (1ul <<  2) /* 0x00000001.edx    */
+#define XEN_SYSCTL_CPU_LEVELCAP_extd_ecx    (1ul <<  3) /* 0x80000001.ecx    */
+#define XEN_SYSCTL_CPU_LEVELCAP_extd_edx    (1ul <<  4) /* 0x80000001.edx    */
+#define XEN_SYSCTL_CPU_LEVELCAP_xsave_eax   (1ul <<  5) /* 0x0000000D:1.eax  */
+#define XEN_SYSCTL_CPU_LEVELCAP_thermal_ecx (1ul <<  6) /* 0x00000006.ecx    */
+#define XEN_SYSCTL_CPU_LEVELCAP_l7s0_eax    (1ul <<  7) /* 0x00000007:0.eax  */
+#define XEN_SYSCTL_CPU_LEVELCAP_l7s0_ebx    (1ul <<  8) /* 0x00000007:0.ebx  */
+    uint32_t caps;
+};
+typedef struct xen_sysctl_cpu_levelling_caps xen_sysctl_cpu_levelling_caps_t;
+DEFINE_XEN_GUEST_HANDLE(xen_sysctl_cpu_levelling_caps_t);
+
 struct xen_sysctl {
     uint32_t cmd;
 #define XEN_SYSCTL_readconsole                    1
@@ -791,6 +812,7 @@ 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_cpu_levelling_caps        25
     uint32_t interface_version; /* XEN_SYSCTL_INTERFACE_VERSION */
     union {
         struct xen_sysctl_readconsole       readconsole;
@@ -816,6 +838,7 @@ 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_cpu_levelling_caps cpu_levelling_caps;
         uint8_t                             pad[128];
     } u;
 };
-- 
2.1.4


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