linux-kernel - Re: [PATCH] x86/smp: Validate APIC ID before parking CPU in INIT

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Message-ID: <87cyzwjbff.ffs@tglx>
Date:   Wed, 09 Aug 2023 20:52:20 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Vasant Hegde <vasant.hegde@....com>, linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, dave.hansen@...ux.intel.com, bp@...en8.de,
        mingo@...hat.com, Vasant Hegde <vasant.hegde@....com>,
        Dheeraj Kumar Srivastava <dheerajkumar.srivastava@....com>
Subject: Re: [PATCH] x86/smp: Validate APIC ID before parking CPU in INIT

On Wed, Aug 09 2023 at 20:42, Thomas Gleixner wrote:
> On Wed, Jul 19 2023 at 05:13, Vasant Hegde wrote:
>> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
>> index e1aa2cd7734b..e5ca0689c4dd 100644
>> --- a/arch/x86/kernel/smpboot.c
>> +++ b/arch/x86/kernel/smpboot.c
>> @@ -1360,7 +1360,7 @@ bool smp_park_other_cpus_in_init(void)
>>  		if (cpu == this_cpu)
>>  			continue;
>>  		apicid = apic->cpu_present_to_apicid(cpu);
>> -		if (apicid == BAD_APICID)
>> +		if (apicid == BAD_APICID || !apic->apic_id_valid(apicid))
>>  			continue;
>>  		send_init_sequence(apicid);
>>  	}

I think this papers over the underlying problem that this sends INIT to
an APIC which was never booted. The below is curing the root cause.

Thanks,

        tglx
---
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1356,7 +1356,7 @@ bool smp_park_other_cpus_in_init(void)
 	if (this_cpu)
 		return false;
 
-	for_each_present_cpu(cpu) {
+	for_each_cpu_and(cpu, &cpus_booted_once_mask, cpu_present_mask) {
 		if (cpu == this_cpu)
 			continue;
 		apicid = apic->cpu_present_to_apicid(cpu);