linux-kernel - Re: [PATCH 3/6] x86/smpboot: Remove initial

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Date:   Thu, 23 Feb 2023 08:05:34 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Brian Gerst <brgerst@...il.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Cc:     Usama Arif <usama.arif@...edance.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 3/6] x86/smpboot: Remove initial_stack on 64-bit

On Wed, 2023-02-22 at 17:12 -0500, Brian Gerst wrote:
> @@ -245,11 +245,11 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
>  #ifdef CONFIG_SMP
>         /*
>          * Is this the boot CPU coming up? If so everything is available
> -        * in initial_gs, initial_stack and early_gdt_descr.
> +        * in initial_gs and early_gdt_descr.
>          */
>         movl    smpboot_control(%rip), %edx
>         testl   $STARTUP_SECONDARY, %edx
> -       jz      .Lsetup_cpu
> +       jz      .Linit_cpu0_data
>  
>         /*
>          * For parallel boot, the APIC ID is retrieved from CPUID, and then
> @@ -302,6 +302,10 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
>         hlt
>         jmp     1b
>  
> +.Linit_cpu0_data:
> +       movq    __per_cpu_offset(%rip), %rdx
> +       jmp     .Lsetup_cpu
> +

Aren't all CPUs taking this .Linit_cpu0_data path for non-parallel
startup, not just cpu0? I think you want something more like

.Linit_cpuN_data:
	orl	$0x0fffffff, %edx
	leaq	__per_cpu_offset(%rip), %rbx
	movq	(%rbx,%rdx,8), %rdx
	jmp	.Lsetup_cpu
 

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