linux-kernel - Re: [PATCH REBASED RESEND] x86/cpu: Move early cpu initialization into a separate translation unit

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Message-ID: <20180622151446.lqqmk6nkzzkb6lew@black.fi.intel.com>
Date:   Fri, 22 Jun 2018 18:14:46 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH REBASED RESEND] x86/cpu: Move early cpu initialization
 into a separate translation unit

On Fri, Jun 22, 2018 at 02:05:47PM +0000, Thomas Gleixner wrote:
> On Tue, 12 Jun 2018, Kirill A. Shutemov wrote:
> 
> > __pgtable_l5_enabled shouldn't be needed after system has booted, we can
> > mark it as __initdata, but it requires preparation.
> > 
> > This patch moves early cpu initialization into a separate translation
> > unit. This limits effect of USE_EARLY_PGTABLE_L5 to less code.
> > 
> > Without the change cpu_init() uses __pgtable_l5_enabled. cpu_init() is
> > not __init function and it leads to section mismatch.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
> 
> Second thoughts.
> 
> The only place where __pgtable_l5_enabled() is used in common.c is in
> early_identify_cpu() which is marked __init. So how is that section
> mismatch triggered?

Yeah, it's not obvious:

cpu_init()
  load_mm_ldt()
    ldt_slot_va()
      LDT_BASE_ADDR
        LDT_PGD_ENTRY
	  pgtable_l5_enabled()

-- 
 Kirill A. Shutemov