libs/guest: introduce helper to check cpu policy compatibility

Such helpers is just a wrapper to the existing
x86_cpu_policies_are_compatible function. This requires building
policy.c from libx86 on user land also.

No user of the interface introduced.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

tools/include/xenctrl.h

@@ -2614,6 +2614,10 @@ int xc_cpu_policy_update_cpuid(xc_interface *xch, xc_cpu_policy_t policy,
 int xc_cpu_policy_update_msrs(xc_interface *xch, xc_cpu_policy_t policy,
                               const xen_msr_entry_t *msrs, uint32_t nr);
 
+/* Compatibility calculations. */
+bool xc_cpu_policy_is_compatible(xc_interface *xch, const xc_cpu_policy_t host,
+                                 const xc_cpu_policy_t guest);
+
 int xc_get_cpu_levelling_caps(xc_interface *xch, uint32_t *caps);
 int xc_get_cpu_featureset(xc_interface *xch, uint32_t index,
                           uint32_t *nr_features, uint32_t *featureset);

tools/libs/guest/Makefile

@@ -40,7 +40,7 @@ $(patsubst %.c,%.opic,$(ELF_SRCS-y)): CFLAGS += -Wno-pointer-sign
 ifeq ($(CONFIG_X86),y) # Add libx86 to the build
 vpath %.c ../../../xen/lib/x86
 
-SRCS-y                 += cpuid.c msr.c
+SRCS-y                 += cpuid.c msr.c policy.c
 endif
 
 # new domain builder

tools/libs/guest/xg_cpuid_x86.c

@@ -860,3 +860,22 @@ int xc_cpu_policy_update_msrs(xc_interface *xch, xc_cpu_policy_t policy,
 
     return rc;
 }
+
+bool xc_cpu_policy_is_compatible(xc_interface *xch, const xc_cpu_policy_t host,
+                                 const xc_cpu_policy_t guest)
+{
+    struct cpu_policy_errors err = INIT_CPU_POLICY_ERRORS;
+    struct cpu_policy h = { &host->cpuid, &host->msr };
+    struct cpu_policy g = { &guest->cpuid, &guest->msr };
+    int rc = x86_cpu_policies_are_compatible(&h, &g, &err);
+
+    if ( !rc )
+        return true;
+
+    if ( err.leaf != -1 )
+        ERROR("Leaf %#x subleaf %#x is not compatible", err.leaf, err.subleaf);
+    if ( err.msr != -1 )
+        ERROR("MSR index %#x is not compatible", err.msr);
+
+    return false;
+}