FAILED: patch "[PATCH] x86/smp: Cure kexec() vs. mwait_play_dead() breakage" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x d7893093a7417527c0d73c9832244e65c9d0114f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023062809-ultimate-spider-e3a0@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d7893093a7417527c0d73c9832244e65c9d0114f Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <[email protected]>
Date: Thu, 15 Jun 2023 22:33:57 +0200
Subject: [PATCH] x86/smp: Cure kexec() vs. mwait_play_dead() breakage

TLDR: It's a mess.

When kexec() is executed on a system with offline CPUs, which are parked in mwait_play_dead() it can end up in a triple fault during the bootup of the kexec kernel or cause hard to diagnose data corruption.

The reason is that kexec() eventually overwrites the previous kernel's text, page tables, data and stack. If it writes to the cache line which is monitored by a previously offlined CPU, MWAIT resumes execution and ends up executing the wrong text, dereferencing overwritten page tables or corrupting the kexec kernels data.

Cure this by bringing the offlined CPUs out of MWAIT into HLT.

Write to the monitored cache line of each offline CPU, which makes MWAIT resume execution. The written control word tells the offlined CPUs to issue HLT, which does not have the MWAIT problem.

That does not help, if a stray NMI, MCE or SMI hits the offlined CPUs as those make it come out of HLT.

A follow up change will put them into INIT, which protects at least against NMI and SMI.

index 4e91054c84be..d4ce5cb5c953 100644
@@ -132,6 +132,8 @@ void wbinvd_on_cpu(int cpu);
 int wbinvd_on_all_cpus(void);
 void cond_wakeup_cpu0(void);
 
+void smp_kick_mwait_play_dead(void);
+
 void native_smp_send_reschedule(int cpu);
 void native_send_call_func_ipi(const struct cpumask *mask);
 void native_send_call_func_single_ipi(int cpu);

index d842875f986f..174d6232b87f 100644
@@ -21,6 +21,7 @@
 #include <linux/interrupt.h>
 #include <linux/cpu.h>
 #include <linux/gfp.h>
+#include <linux/kexec.h>
 
 #include <asm/mtrr.h>
 #include <asm/tlbflush.h>

@@ -157,6 +158,10 @@ static void native_stop_other_cpus(int wait)
 	if (atomic_cmpxchg(&stopping_cpu, -1, cpu) != -1)
 		return;
 
+	/* For kexec, ensure that offline CPUs are out of MWAIT and in HLT */
+	if (kexec_in_progress)
+		smp_kick_mwait_play_dead();
+
 	/*
 	 * 1) Send an IPI on the reboot vector to all other CPUs.
 	 *