x86/cpu: Load microcode during restore_processor_state()

When resuming from system sleep state, restore_processor_state()
restores the boot CPU MSRs. These MSRs could be emulated by microcode.
If microcode is not loaded yet, writing to emulated MSRs leads to
unchecked MSR access error:

  ...
  PM: Calling lapic_suspend+0x0/0x210
  unchecked MSR access error: WRMSR to 0x10f (tried to write 0x0...0) at rIP: ... (native_write_msr)
  Call Trace:
    <TASK>
    ? restore_processor_state
    x86_acpi_suspend_lowlevel
    acpi_suspend_enter
    suspend_devices_and_enter
    pm_suspend.cold
    state_store
    kobj_attr_store
    sysfs_kf_write
    kernfs_fop_write_iter
    new_sync_write
    vfs_write
    ksys_write
    __x64_sys_write
    do_syscall_64
    entry_SYSCALL_64_after_hwframe
   RIP: 0033:0x7fda13c260a7

To ensure microcode emulated MSRs are available for restoration, load
the microcode on the boot CPU before restoring these MSRs.

  [ Pawan: write commit message and productize it. ]

Fixes: e2a1256 ("x86/speculation: Restore speculation related MSRs during S3 resume")
Reported-by: Kyle D. Pelton <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Signed-off-by: Pawan Gupta <[email protected]>
Tested-by: Kyle D. Pelton <[email protected]>
Cc: [email protected]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215841
Link: https://lore.kernel.org/r/4350dfbf785cd482d3fafa72b2b49c83102df3ce.1650386317.git.pawan.kumar.gupta@linux.intel.com

arch/x86/include/asm/microcode.h

@@ -131,10 +131,12 @@ extern void __init load_ucode_bsp(void);
 extern void load_ucode_ap(void);
 void reload_early_microcode(void);
 extern bool initrd_gone;
+void microcode_bsp_resume(void);
 #else
 static inline void __init load_ucode_bsp(void)			{ }
 static inline void load_ucode_ap(void)				{ }
 static inline void reload_early_microcode(void)			{ }
+static inline void microcode_bsp_resume(void)			{ }
 #endif
 
 #endif /* _ASM_X86_MICROCODE_H */

arch/x86/kernel/cpu/microcode/core.c

@@ -758,9 +758,9 @@ static struct subsys_interface mc_cpu_interface = {
 };
 
 /**
- * mc_bp_resume - Update boot CPU microcode during resume.
+ * microcode_bsp_resume - Update boot CPU microcode during resume.
  */
-static void mc_bp_resume(void)
+void microcode_bsp_resume(void)
 {
 	int cpu = smp_processor_id();
 	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
@@ -772,7 +772,7 @@ static void mc_bp_resume(void)
 }
 
 static struct syscore_ops mc_syscore_ops = {
-	.resume			= mc_bp_resume,
+	.resume			= microcode_bsp_resume,
 };
 
 static int mc_cpu_starting(unsigned int cpu)

arch/x86/power/cpu.c

@@ -25,6 +25,7 @@
 #include <asm/cpu.h>
 #include <asm/mmu_context.h>
 #include <asm/cpu_device_id.h>
+#include <asm/microcode.h>
 
 #ifdef CONFIG_X86_32
 __visible unsigned long saved_context_ebx;
@@ -262,11 +263,18 @@ static void notrace __restore_processor_state(struct saved_context *ctxt)
 	x86_platform.restore_sched_clock_state();
 	mtrr_bp_restore();
 	perf_restore_debug_store();
-	msr_restore_context(ctxt);
 
 	c = &cpu_data(smp_processor_id());
 	if (cpu_has(c, X86_FEATURE_MSR_IA32_FEAT_CTL))
 		init_ia32_feat_ctl(c);
+
+	microcode_bsp_resume();
+
+	/*
+	 * This needs to happen after the microcode has been updated upon resume
+	 * because some of the MSRs are "emulated" in microcode.
+	 */
+	msr_restore_context(ctxt);
 }
 
 /* Needed by apm.c */