linux-kernel - Re: [patch V3 02/40] x86/apic: Fake primary thread mask for XEN/PV

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Date:   Fri, 04 Aug 2023 22:02:59 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Borislav Petkov <bp@...en8.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Tom Lendacky <thomas.lendacky@....com>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Huang Rui <ray.huang@....com>, Juergen Gross <jgross@...e.com>,
        Dimitri Sivanich <dimitri.sivanich@....com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>
Subject: Re: [patch V3 02/40] x86/apic: Fake primary thread mask for XEN/PV

On Fri, Aug 04 2023 at 20:12, Borislav Petkov wrote:
>> @@ -2344,6 +2346,15 @@ static int __init smp_init_primary_threa
>>  {
>>  	unsigned int cpu;
>>  
>> +	/*
>> +	 * XEN/PV provides either none or useless topology information.
>> +	 * Pretend that all vCPUs are primary threads.
>> +	 */
>> +	if (xen_pv_domain()) {
>> +		cpumask_copy(&__cpu_primary_thread_mask, cpu_possible_mask);
>> +		return 0;
>> +	}
>
> Can this be somewhere in the Xen init code instead?

Not for now. That's all going away with the 3rd installment. But right
now it's the right place to be.