x86/microcode: Add a parameter to microcode_check() to store CPU capabilities

Add a parameter to store CPU capabilities before performing a microcode
update so that CPU capabilities can be compared before and after update.

  [ bp: Massage. ]

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230109153555.4986-2-ashok.raj@intel.com

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 4e35c66..f256a4d 100644 (file)
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -697,7 +697,7 @@ bool xen_set_default_idle(void);
 #endif
 
 void __noreturn stop_this_cpu(void *dummy);
-void microcode_check(void);
+void microcode_check(struct cpuinfo_x86 *prev_info);
 
 enum l1tf_mitigations {
        L1TF_MITIGATION_OFF,

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 9cfca3d..0f5a173 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2297,30 +2297,35 @@ void cpu_init_secondary(void)
 #endif
 
 #ifdef CONFIG_MICROCODE_LATE_LOADING
-/*
+/**
+ * microcode_check() - Check if any CPU capabilities changed after an update.
+ * @prev_info: CPU capabilities stored before an update.
+ *
  * The microcode loader calls this upon late microcode load to recheck features,
  * only when microcode has been updated. Caller holds microcode_mutex and CPU
  * hotplug lock.
+ *
+ * Return: None
  */
-void microcode_check(void)
+void microcode_check(struct cpuinfo_x86 *prev_info)
 {
-       struct cpuinfo_x86 info;
-
        perf_check_microcode();
 
        /* Reload CPUID max function as it might've changed. */
-       info.cpuid_level = cpuid_eax(0);
+       prev_info->cpuid_level = cpuid_eax(0);
 
        /*
         * Copy all capability leafs to pick up the synthetic ones so that
         * memcmp() below doesn't fail on that. The ones coming from CPUID will
         * get overwritten in get_cpu_cap().
         */
-       memcpy(&info.x86_capability, &boot_cpu_data.x86_capability, sizeof(info.x86_capability));
+       memcpy(&prev_info->x86_capability, &boot_cpu_data.x86_capability,
+              sizeof(prev_info->x86_capability));
 
-       get_cpu_cap(&info);
+       get_cpu_cap(prev_info);
 
-       if (!memcmp(&info.x86_capability, &boot_cpu_data.x86_capability, sizeof(info.x86_capability)))
+       if (!memcmp(&prev_info->x86_capability, &boot_cpu_data.x86_capability,
+                   sizeof(prev_info->x86_capability)))
                return;
 
        pr_warn("x86/CPU: CPU features have changed after loading microcode, but might not take effect.\n");

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 99abb31..dc5dfba 100644 (file)
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -438,6 +438,7 @@ wait_for_siblings:
 static int microcode_reload_late(void)
 {
        int old = boot_cpu_data.microcode, ret;
+       struct cpuinfo_x86 prev_info;
 
        pr_err("Attempting late microcode loading - it is dangerous and taints the kernel.\n");
        pr_err("You should switch to early loading, if possible.\n");
@@ -447,7 +448,7 @@ static int microcode_reload_late(void)
 
        ret = stop_machine_cpuslocked(__reload_late, NULL, cpu_online_mask);
        if (ret == 0)
-               microcode_check();
+               microcode_check(&prev_info);
 
        pr_info("Reload completed, microcode revision: 0x%x -> 0x%x\n",
                old, boot_cpu_data.microcode);