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Date: Fri, 12 Jun 2015 23:12:20 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mml@vger.kernel.org,
        Andy Lutomirski <luto@amacapital.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Denys Vlasenko <dvlasenk@redhat.com>, Brian Gerst <brgerst@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, Waiman Long <Waiman.Long@hp.com>
Subject: Re: [PATCH 05/12] mm: Introduce arch_pgd_init_late()
Message-ID: <20150612211220.GC18966@redhat.com>
References: <1434031637-9091-1-git-send-email-mingo@kernel.org> <1434031637-9091-6-git-send-email-mingo@kernel.org>
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On 06/11, Ingo Molnar wrote:
>
> @@ -1592,6 +1592,22 @@ static struct task_struct *copy_process(unsigned long clone_flags,
>  	syscall_tracepoint_update(p);
>  	write_unlock_irq(&tasklist_lock);
>  
> +	/*
> +	 * If we have a new PGD then initialize it:
> +	 *
> +	 * This method is called after a task has been made visible
> +	 * on the task list already.
> +	 *
> +	 * Architectures that manage per task kernel pagetables
> +	 * might use this callback to initialize them after they
> +	 * are already visible to new updates.
> +	 *
> +	 * NOTE: any user-space parts of the PGD are already initialized
> +	 *       and must not be clobbered.
> +	 */
> +	if (p->mm != current->mm)
> +		arch_pgd_init_late(p->mm, p->mm->pgd);
> +

Cosmetic, but imo

	if (!(clone_flags & CLONE_VM))
		arch_pgd_init_late(...);

will look better and more consistent.

Oleg.