linux-kernel - [patch V5 19/39] x86/microcode: Remove pointless apply() invocation

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Date:   Tue, 17 Oct 2023 23:23:49 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Borislav Petkov <bp@...en8.de>
Subject: [patch V5 19/39] x86/microcode: Remove pointless apply() invocation

From: Thomas Gleixner <tglx@...utronix.de>

Microcode is applied on the APs during early bringup. There is no point
in trying to apply the microcode again during the hotplug operations and
neither at the point where the microcode device is initialized.

Collect CPU info and microcode revision in setup_online_cpu() for now.
This will move to the CPU hotplug callback later.

[ bp: Leave the starting notifier for the following scenario:

    - boot, late load, suspend to disk, resume

    without the starting notifier, only the last core manages to update the
    microcode upon resume:

    # rdmsr -a 0x8b
    10000bf
    10000bf
    10000bf
    10000bf
    10000bf
    10000dc <----

    This is on an AMD F10h machine.

    For the future, one should check whether potential unification of
    the CPU init path could cover the resume path too so that this can
    be simplified even more.

 tglx: This is caused by the odd handling of APs which try to find the
       microcode blob in builtin or initrd instead of caching the microcode
       blob during early init before the APs are brought up. Will be
       cleaned up in a later step. ]

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
V5: Drop the starting notifier change as that requires rework of the
    AMD code.
---
 arch/x86/kernel/cpu/microcode/core.c |   23 ++++++-----------------
 1 file changed, 6 insertions(+), 17 deletions(-)
---
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -487,17 +487,6 @@ static void microcode_fini_cpu(int cpu)
 		microcode_ops->microcode_fini_cpu(cpu);
 }
 
-static enum ucode_state microcode_init_cpu(int cpu)
-{
-	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
-
-	memset(uci, 0, sizeof(*uci));
-
-	microcode_ops->collect_cpu_info(cpu, &uci->cpu_sig);
-
-	return microcode_ops->apply_microcode(cpu);
-}
-
 /**
  * microcode_bsp_resume - Update boot CPU microcode during resume.
  */
@@ -552,14 +541,14 @@ static int mc_cpu_down_prep(unsigned int
 static void setup_online_cpu(struct work_struct *work)
 {
 	int cpu = smp_processor_id();
-	enum ucode_state err;
+	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 
-	err = microcode_init_cpu(cpu);
-	if (err == UCODE_ERROR) {
-		pr_err("Error applying microcode on CPU%d\n", cpu);
-		return;
-	}
+	memset(uci, 0, sizeof(*uci));
 
+	microcode_ops->collect_cpu_info(cpu, &uci->cpu_sig);
+	cpu_data(cpu).microcode = uci->cpu_sig.rev;
+	if (!cpu)
+		boot_cpu_data.microcode = uci->cpu_sig.rev;
 	mc_cpu_online(cpu);
 }