linux-kernel - Re: [patch V2 16/58] x86/apic: Sanitize num

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Date:   Tue, 1 Aug 2023 08:12:36 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Andrew Cooper <andrew.cooper3@...rix.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Wei Liu <wei.liu@...nel.org>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Peter Keresztes Schmidt <peter@...esztesschmidt.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: Re: [patch V2 16/58] x86/apic: Sanitize num_processors handling

On 31.07.23 20:19, Juergen Gross wrote:
> On 31.07.23 17:57, Thomas Gleixner wrote:
>> On Mon, Jul 31 2023 at 14:50, Thomas Gleixner wrote:
>>> Why can't XENPV pretend that it has a smp configuration detected,
>>> i.e. setting smp_found_config as any other special get_smp_config()
>>> implementation does?
>>
>> The below should do the trick, no?
> 
> Something like that, yes.
> 
> I'm just hunting another regression in the series. With patch 23 of the
> topology series applied the APs of a Xen PV guests won't be onlined. I
> guess this is due to missing topology data initialization somewhere in
> the Xen related code.
> 
> I'll check your suggestion after finding the reason for the regression.
> 
>>
>>
>> --- a/arch/x86/xen/smp_pv.c
>> +++ b/arch/x86/xen/smp_pv.c
>> @@ -182,7 +182,8 @@ static void __init _get_smp_config(unsig
>>       if (subtract)
>>           set_nr_cpu_ids(nr_cpu_ids - subtract);
>>   #endif
>> -
>> +    /* Pretend to be a proper enumerated system */
>> +    smp_found_config = 1;
>>   }
>>   static void __init xen_pv_smp_prepare_boot_cpu(void)
> 

It is working fine.


Juergen

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