linux-kernel - Re: [tip:x86/urgent] [x86/kaslr] dfb3911c36: kernel_BUG_at

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Message-ID: <87seuzjm4b.ffs@tglx>
Date: Tue, 20 Aug 2024 16:37:56 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: kernel test robot <oliver.sang@...el.com>
Cc: oe-lkp@...ts.linux.dev, lkp@...el.com, linux-kernel@...r.kernel.org,
 x86@...nel.org, Max Ramanouski <max8rr8@...il.com>, Alistair Popple
 <apopple@...dia.com>, Dan Williams <dan.j.williams@...el.com>, Kees Cook
 <kees@...nel.org>, linux-mm@...ck.org, oliver.sang@...el.com
Subject: Re: [tip:x86/urgent] [x86/kaslr]  dfb3911c36:
 kernel_BUG_at_arch/x86/mm/physaddr.c

On Tue, Aug 20 2024 at 13:57, Thomas Gleixner wrote:
> On Tue, Aug 20 2024 at 15:16, kernel test robot wrote:
>  		/*
>  		 * KASLR trims the maximum possible size of the
>  		 * direct-map. Update the physmem_end boundary.
> +		 * No rounding required as the region starts
> +		 * PUD aligned and size is in units of TB.
>  		 */
>  		if (kaslr_regions[i].end)
> -			*kaslr_regions[i].end = __pa(vaddr) - 1;
> +			*kaslr_regions[i].end = __pa_nodebug(vaddr - 1);
> +
> +		/* Add a minimum padding based on randomization alignment. */
> +		vaddr = round_up(vaddr + 1, PUD_SIZE);

Due to the guaranteed PUD alignment of vaddr this round_up() is actually
pointless and just should be

		vaddr += PUD_SIZE;

No?

Thanks,

        tglx