[PATCH] x86/ucode: Refresh raw CPU policy after microcode load

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Loading microcode can cause new features to appear.  This has happened
routinely since Spectre/Meltdown, and even the presence of new status bits can
mean the administrator has no further work to perform.

Refresh the raw CPU policy after late microcode load, so xen-cpuid can reflect
the updated state of the system.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>

This is also the first step of being able to livepatch support for new
functionality in microcode.
---
 xen/arch/x86/cpu-policy.c             | 6 +++---
 xen/arch/x86/cpu/microcode/core.c     | 4 ++++
 xen/arch/x86/include/asm/cpu-policy.h | 6 ++++++
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/cpu-policy.c b/xen/arch/x86/cpu-policy.c
index a58bf6cad54e..ef6a2d0d180a 100644
--- a/xen/arch/x86/cpu-policy.c
+++ b/xen/arch/x86/cpu-policy.c
@@ -15,7 +15,7 @@
 #include <asm/setup.h>
 #include <asm/xstate.h>
 
-struct cpu_policy __ro_after_init     raw_cpu_policy;
+struct cpu_policy __read_mostly       raw_cpu_policy;
 struct cpu_policy __ro_after_init    host_cpu_policy;
 #ifdef CONFIG_PV
 struct cpu_policy __ro_after_init  pv_max_cpu_policy;
@@ -343,7 +343,7 @@ static void recalculate_misc(struct cpu_policy *p)
     }
 }
 
-static void __init calculate_raw_policy(void)
+void calculate_raw_cpu_policy(void)
 {
     struct cpu_policy *p = &raw_cpu_policy;
 
@@ -655,7 +655,7 @@ static void __init calculate_hvm_def_policy(void)
 
 void __init init_guest_cpu_policies(void)
 {
-    calculate_raw_policy();
+    calculate_raw_cpu_policy();
     calculate_host_policy();
 
     if ( IS_ENABLED(CONFIG_PV) )
diff --git a/xen/arch/x86/cpu/microcode/core.c 
b/xen/arch/x86/cpu/microcode/core.c
index 61cd36d601d6..cd456c476fbf 100644
--- a/xen/arch/x86/cpu/microcode/core.c
+++ b/xen/arch/x86/cpu/microcode/core.c
@@ -34,6 +34,7 @@
 #include <xen/watchdog.h>
 
 #include <asm/apic.h>
+#include <asm/cpu-policy.h>
 #include <asm/delay.h>
 #include <asm/nmi.h>
 #include <asm/processor.h>
@@ -677,6 +678,9 @@ static long cf_check microcode_update_helper(void *data)
         spin_lock(&microcode_mutex);
         microcode_update_cache(patch);
         spin_unlock(&microcode_mutex);
+
+        /* Refresh the raw CPU policy, in case the features have changed. */
+        calculate_raw_cpu_policy();
     }
     else
         microcode_free_patch(patch);
diff --git a/xen/arch/x86/include/asm/cpu-policy.h 
b/xen/arch/x86/include/asm/cpu-policy.h
index b361537a602b..99d5a8e67eeb 100644
--- a/xen/arch/x86/include/asm/cpu-policy.h
+++ b/xen/arch/x86/include/asm/cpu-policy.h
@@ -24,4 +24,10 @@ void init_dom0_cpuid_policy(struct domain *d);
 /* Clamp the CPUID policy to reality. */
 void recalculate_cpuid_policy(struct domain *d);
 
+/*
+ * Collect the raw CPUID and MSR values.  Called during boot, and after late
+ * microcode loading.
+ */
+void calculate_raw_cpu_policy(void);
+
 #endif /* X86_CPU_POLICY_H */
-- 
2.30.2