linux-kernel - [Part 2 v2[cleanup] 4/4] x86/microcode: Do not call apply

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Message-Id: <20230121213512.251578-5-ashok.raj@intel.com>
Date:   Sat, 21 Jan 2023 13:35:12 -0800
From:   Ashok Raj <ashok.raj@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>
Cc:     Ashok Raj <ashok.raj@...el.com>,
        LKML <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Alison Schofield <alison.schofield@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Stefan Talpalaru <stefantalpalaru@...oo.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Jonathan Corbet <corbet@....net>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Peter Zilstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Martin Pohlack <mpohlack@...zon.de>
Subject: [Part 2 v2[cleanup] 4/4] x86/microcode: Do not call apply_microde() on sibling threads

Microcode updates are applied at the core, and both threads of HT siblings
will notice the update.

During late-load, after the primary has updated the microcode, it also
reflects that in the per-cpu structure (cpuinfo_x86) holding the current
revision.

Since the sibling hasn't had a chance to update the per-cpu revision,
the current code calls apply_microcode() just as a way to verify and also
update the per-cpu revision number.

But in the odd case when primary returned with an error, the secondary will
try to perform a patchload and the primary has already been released to the
system. This could be problematic.

Replace apply_microcode() with a call to collect_cpu_info() and let that
call also update the per-cpu structure instead of returning the previously
cached values.

Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ashok Raj <ashok.raj@...el.com>
Cc: LKML <linux-kernel@...r.kernel.org>
Cc: x86 <x86@...nel.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Tony Luck <tony.luck@...el.com>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Alison Schofield <alison.schofield@...el.com>
Cc: Reinette Chatre <reinette.chatre@...el.com>
Cc: Thomas Gleixner (Intel) <tglx@...utronix.de>
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Stefan Talpalaru <stefantalpalaru@...oo.com>
Cc: David Woodhouse <dwmw2@...radead.org>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Jonathan Corbet <corbet@....net>
Cc: Rafael J. Wysocki <rafael@...nel.org>
Cc: Peter Zilstra (Intel) <peterz@...radead.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Andrew Cooper <Andrew.Cooper3@...rix.com>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Martin Pohlack <mpohlack@...zon.de>
---
 arch/x86/kernel/cpu/microcode/core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 6ade3d59c404..089636b1643f 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -386,6 +386,7 @@ static int __wait_for_cpus(atomic_t *t, long long timeout)
  */
 static int __reload_late(void *info)
 {
+	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 	int cpu = smp_processor_id();
 	enum ucode_state err;
 	int ret = 0;
@@ -422,12 +423,11 @@ static int __reload_late(void *info)
 
 	/*
 	 * At least one thread has completed update on each core.
-	 * For others, simply call the update to make sure the
-	 * per-cpu cpuinfo can be updated with right microcode
-	 * revision.
+	 * For siblings, collect the cpuinfo and update the
+	 * per-cpu cpuinfo with the current microcode revision.
 	 */
 	if (cpumask_first(topology_sibling_cpumask(cpu)) != cpu)
-		err = microcode_ops->apply_microcode(cpu);
+		microcode_ops->collect_cpu_info(cpu, &uci->cpu_sig);
 
 	return ret;
 }
-- 
2.34.1