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Re: [XEN PATCH 8/9] x86/smp: make cpu_state per-CPU


  • To: Krystian Hebel <krystian.hebel@xxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Wed, 13 Mar 2024 14:21:09 +0100
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  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • Delivery-date: Wed, 13 Mar 2024 13:21:25 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 12.03.2024 17:38, Krystian Hebel wrote:
> On 8.02.2024 13:13, Jan Beulich wrote:
>> On 14.11.2023 18:50, Krystian Hebel wrote:
>>> @@ -320,6 +317,10 @@ void start_secondary(unsigned int cpu)
>>>   
>>>       /* Critical region without IDT or TSS.  Any fault is deadly! */
>>>   
>>> +    /* Wait until data set up by CPU_UP_PREPARE notifiers is ready. */
>>> +    while ( cpu_data[cpu].cpu_state != CPU_STATE_CALLOUT )
>>> +        cpu_relax();
>> I'm afraid I don't understand the comment (and hence whether this loop
>> is actually needed here): __cpu_up() is called only after those
>> notifiers completed.
> Yes, but broadcasted INIT-SIPI-SIPI sequence added in next patch will be
> sent before that call is made, and consequently APs potentially can get
> to this point before that data is set up.

That's fine, and I was able to conclude this once having read that following
patch. But the patch here, including its description, wants to the self-
contained.

Jan



 


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