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From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
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	Peter Zijlstra <peterz@infradead.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
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	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: [PATCHv6 14/16] x86/smp: Add smp_ops.stop_this_cpu() callback
Date: Wed, 24 Jan 2024 14:55:55 +0200
Message-ID: <20240124125557.493675-15-kirill.shutemov@linux.intel.com>
In-Reply-To: <20240124125557.493675-1-kirill.shutemov@linux.intel.com>
References: <20240124125557.493675-1-kirill.shutemov@linux.intel.com>
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If the helper is defined, it is called instead of halt() to stop the CPU
at the end of stop_this_cpu() and on crash CPU shutdown.

ACPI MADT will use it to hand over the CPU to BIOS in order to be able
to wake it up again after kexec.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/asm/smp.h | 1 +
 arch/x86/kernel/process.c  | 7 +++++++
 arch/x86/kernel/reboot.c   | 6 ++++++
 3 files changed, 14 insertions(+)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 4fab2ed454f3..390d53fd34f9 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -38,6 +38,7 @@ struct smp_ops {
 	int (*cpu_disable)(void);
 	void (*cpu_die)(unsigned int cpu);
 	void (*play_dead)(void);
+	void (*stop_this_cpu)(void);
 
 	void (*send_call_func_ipi)(const struct cpumask *mask);
 	void (*send_call_func_single_ipi)(int cpu);
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index ab49ade31b0d..00c1b957476d 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -835,6 +835,13 @@ void __noreturn stop_this_cpu(void *dummy)
 	 */
 	cpumask_clear_cpu(cpu, &cpus_stop_mask);
 
+#ifdef CONFIG_SMP
+	if (smp_ops.stop_this_cpu) {
+		smp_ops.stop_this_cpu();
+		unreachable();
+	}
+#endif
+
 	for (;;) {
 		/*
 		 * Use native_halt() so that memory contents don't change
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 0574d4ad6b41..0a75efe579c0 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -880,6 +880,12 @@ static int crash_nmi_callback(unsigned int val, struct pt_regs *regs)
 	cpu_emergency_disable_virtualization();
 
 	atomic_dec(&waiting_for_crash_ipi);
+
+	if (smp_ops.stop_this_cpu) {
+		smp_ops.stop_this_cpu();
+		unreachable();
+	}
+
 	/* Assume hlt works */
 	halt();
 	for (;;)
-- 
2.43.0