[PATCH RFC 6/7] x86: cpu: bugs.c: reprobe bugs at runtime

[Mihai Carabas]

Adapt check_bugs to be callable at runtime after the
microcode late loading has been done.

Also update SRBDS to reset the default value for srbds_mitigation and call
update_srbds_msr on all CPUs.

Signed-off-by: Mihai Carabas <mihai.cara...@oracle.com>
---
 arch/x86/kernel/cpu/bugs.c           | 37 ++++++++++++++++++++++++++----------
 arch/x86/kernel/cpu/microcode/core.c |  2 ++
 2 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 21b9df3..c4084d7 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -77,17 +77,19 @@
 
 void __ref check_bugs(void)
 {
-       identify_boot_cpu();
+       if (system_state != SYSTEM_RUNNING) {
+               identify_boot_cpu();
 
-       /*
-        * identify_boot_cpu() initialized SMT support information, let the
-        * core code know.
-        */
-       cpu_smt_check_topology();
+               /*
+                * identify_boot_cpu() initialized SMT support information,
+                * let the core code know.
+                */
+               cpu_smt_check_topology();
 
-       if (!IS_ENABLED(CONFIG_SMP)) {
-               pr_info("CPU: ");
-               print_cpu_info(&boot_cpu_data);
+               if (!IS_ENABLED(CONFIG_SMP)) {
+                       pr_info("CPU: ");
+                       print_cpu_info(&boot_cpu_data);
+               }
        }
 
        /*
@@ -112,6 +114,13 @@ void __ref check_bugs(void)
        srbds_select_mitigation();
 
        /*
+        * If we are late loading the microcode, code below should
+        * not be executed --- it is only needed during boot.
+        */
+       if (system_state == SYSTEM_RUNNING)
+               return;
+
+       /*
         * As MDS and TAA mitigations are inter-related, print MDS
         * mitigation until after TAA mitigation selection is done.
         */
@@ -452,10 +461,17 @@ void update_srbds_msr(void)
        wrmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);
 }
 
+static void _update_srbds_msr(void *p)
+{
+       update_srbds_msr();
+}
+
 static void srbds_select_mitigation(void)
 {
        u64 ia32_cap;
 
+       srbds_mitigation = SRBDS_MITIGATION_FULL;
+
        if (!boot_cpu_has_bug(X86_BUG_SRBDS))
                return;
 
@@ -473,7 +489,8 @@ static void srbds_select_mitigation(void)
        else if (cpu_mitigations_off() || srbds_off)
                srbds_mitigation = SRBDS_MITIGATION_OFF;
 
-       update_srbds_msr();
+       on_each_cpu(_update_srbds_msr, NULL, 1);
+
        pr_info("%s\n", srbds_strings[srbds_mitigation]);
 }
 
diff --git a/arch/x86/kernel/cpu/microcode/core.c 
b/arch/x86/kernel/cpu/microcode/core.c
index 2cd983a..6d327a0 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -31,6 +31,7 @@
 #include <linux/fs.h>
 #include <linux/mm.h>
 
+#include <asm/bugs.h>
 #include <asm/microcode_intel.h>
 #include <asm/cpu_device_id.h>
 #include <asm/microcode_amd.h>
@@ -669,6 +670,7 @@ static ssize_t reload_store(struct device *dev,
 
        mutex_lock(&microcode_mutex);
        ret = microcode_reload_late();
+       check_bugs();
        mutex_unlock(&microcode_mutex);
 
 put:
-- 
1.8.3.1