Re: [patch 35/37] x86/smpboot: Support parallel startup of secondary CPUs

[Thomas Gleixner]

On Sat, Apr 15 2023 at 09:22, Brian Gerst wrote:
> On Fri, Apr 14, 2023 at 7:45 PM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>> @@ -248,10 +311,20 @@ SYM_INNER_LABEL(secondary_startup_64_no_
>>          *
>>          * RDX contains the per-cpu offset
>>          */
>> -       movq    pcpu_hot + X86_current_task(%rdx), %rax
>> -       movq    TASK_threadsp(%rax), %rsp
>> +       movq    pcpu_hot + X86_top_of_stack(%rdx), %rsp
>
> Switching to using pcpu_hot.top_of_stack is ok, but it's not
> completely equivalent.  top_of_stack points to the end of the pt_regs
> structure, while the kernel stack starts below pt_regs even for kernel
> threads.  So you need to subtract PTREGS_SIZE from the stack pointer
> after this.
>
> This change should also be a separate patch.

You're right on both counts.