[PATCH v3 1/6] x86/microcode: Add a parameter to microcode_check() to store CPU capabilities

From: Ashok Raj
Date: Tue Jan 03 2023 - 13:02:52 EST


This is a preparation before the next patch uses this to compare CPU
capabilities after performing an update.

Add a parameter to store CPU capabilities before performing a microcode
update.

Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: LKML <linux-kernel@xxxxxxxxxxxxxxx>
Cc: x86 <x86@xxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Alison Schofield <alison.schofield@xxxxxxxxx>
Cc: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
arch/x86/include/asm/processor.h | 2 +-
arch/x86/kernel/cpu/common.c | 12 +++++-------
arch/x86/kernel/cpu/microcode/core.c | 3 ++-
3 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 4e35c66edeb7..387578049de0 100644
--- 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 *info);

enum l1tf_mitigations {
L1TF_MITIGATION_OFF,
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 9cfca3d7d0e2..b9c7529c920e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2302,25 +2302,23 @@ void cpu_init_secondary(void)
* only when microcode has been updated. Caller holds microcode_mutex and CPU
* hotplug lock.
*/
-void microcode_check(void)
+void microcode_check(struct cpuinfo_x86 *info)
{
- struct cpuinfo_x86 info;
-
perf_check_microcode();

/* Reload CPUID max function as it might've changed. */
- info.cpuid_level = cpuid_eax(0);
+ 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(&info->x86_capability, &boot_cpu_data.x86_capability, sizeof(info->x86_capability));

- get_cpu_cap(&info);
+ get_cpu_cap(info);

- if (!memcmp(&info.x86_capability, &boot_cpu_data.x86_capability, sizeof(info.x86_capability)))
+ if (!memcmp(&info->x86_capability, &boot_cpu_data.x86_capability, sizeof(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 c4cd7328177b..d86a4f910a6b 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -439,6 +439,7 @@ static int __reload_late(void *info)
static int microcode_reload_late(void)
{
int old = boot_cpu_data.microcode, ret;
+ struct cpuinfo_x86 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");
@@ -448,7 +449,7 @@ static int microcode_reload_late(void)

ret = stop_machine_cpuslocked(__reload_late, NULL, cpu_online_mask);
if (ret == 0)
- microcode_check();
+ microcode_check(&info);

pr_info("Reload completed, microcode revision: 0x%x -> 0x%x\n",
old, boot_cpu_data.microcode);
--
2.34.1