linux-kernel - Re: [PATCH] x86/efi: page align EFI ROM image ranges

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Message-ID: <20170804120650.GE8187@codeblueprint.co.uk>
Date:   Fri, 4 Aug 2017 13:06:50 +0100
From:   Matt Fleming <matt@...eblueprint.co.uk>
To:     Stuart Hayes <stuart.w.hayes@...il.com>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        linux-efi@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] x86/efi: page align EFI ROM image ranges

On Wed, 02 Aug, at 11:41:38AM, Stuart Hayes wrote:
> (Resend because I mistyped the maintainer's email address the first time.)
> 
> The kernel's EFI stub locates and copies EFI ROM images into memory,
> which it allocates using the byte-granular EFI allocate_pool
> function.  These memory ranges are then added to setup_data, and
> later to e820 (in e820__reserve_setup_data()).  The e820 ranges are
> parsed to create nosave regions (in
> e820__register_nosave_regions()), but when non-page-aligned e820
> regions are parsed, a nosave page is added at the beginning and end
> of each non-page-aligned region, which results in data not getting
> saved or restored during a hibernate/resume.  This can result in
> random failures after a hibernate/resume.
>  
> Round up the allocation size to a whole number of pages, and use EFI
> allocate_pages to ensure that the EFI ROM copy regions are
> page-aligned.
> 
> On a system with six EFI ROM images, before the patch:
> 
> e820: update [mem 0x64866020-0x6486e05f] usable ==> usable
> e820: update [mem 0x6147a020-0x61499c5f] usable ==> usable
> e820: update [mem 0x60fff020-0x6105785f] usable ==> usable
> e820: update [mem 0x60fa6020-0x60ffe85f] usable ==> usable
> e820: update [mem 0x60f4d020-0x60fa585f] usable ==> usable
> e820: update [mem 0x60ef4020-0x60f4c85f] usable ==> usable
> ...
> PM: Registered nosave memory: [mem 0x00000000-0x00000fff]
> PM: Registered nosave memory: [mem 0x000a0000-0x000fffff]
> PM: Registered nosave memory: [mem 0x60ef4000-0x60ef4fff]
> PM: Registered nosave memory: [mem 0x60f4c000-0x60f4cfff]
> PM: Registered nosave memory: [mem 0x60f4d000-0x60f4dfff]
> PM: Registered nosave memory: [mem 0x60fa5000-0x60fa5fff]
> PM: Registered nosave memory: [mem 0x60fa6000-0x60fa6fff]
> PM: Registered nosave memory: [mem 0x60ffe000-0x60ffefff]
> PM: Registered nosave memory: [mem 0x60fff000-0x60ffffff]
> PM: Registered nosave memory: [mem 0x61057000-0x61057fff]
> PM: Registered nosave memory: [mem 0x6147a000-0x6147afff]
> PM: Registered nosave memory: [mem 0x61499000-0x61499fff]
> PM: Registered nosave memory: [mem 0x64866000-0x64866fff]
> PM: Registered nosave memory: [mem 0x6486e000-0x6486efff]
> PM: Registered nosave memory: [mem 0x6cf6e000-0x6f3ccfff]
> 
> After the patch:
> 
> e820: update [mem 0x64866000-0x6486efff] usable ==> usable
> e820: update [mem 0x6147a000-0x61499fff] usable ==> usable
> e820: update [mem 0x60fff000-0x61057fff] usable ==> usable
> e820: update [mem 0x60fa6000-0x60ffefff] usable ==> usable
> e820: update [mem 0x60f4d000-0x60fa5fff] usable ==> usable
> e820: update [mem 0x60ef4000-0x60f4cfff] usable ==> usable
> ...
> PM: Registered nosave memory: [mem 0x00000000-0x00000fff]
> PM: Registered nosave memory: [mem 0x000a0000-0x000fffff]
> PM: Registered nosave memory: [mem 0x6cf6e000-0x6f3ccfff]
> 
> Signed-off-by: Stuart Hayes <stuart.w.hayes@...il.com>
> ---
> 
> --- linux-4.13-rc2/arch/x86/boot/compressed/eboot.c.orig	2017-08-01 12:12:04.696049106 -0400
> +++ linux-4.13-rc2/arch/x86/boot/compressed/eboot.c	2017-08-01 12:11:33.120182236 -0400
> @@ -235,7 +235,12 @@ __setup_efi_pci64(efi_pci_io_protocol_64
>  
>  	size = pci->romsize + sizeof(*rom);
>  
> -	status = efi_call_early(allocate_pool, EFI_LOADER_DATA, size, &rom);
> +	/*
> +	 * Get whole pages because this will be added to e820.
> +	 */
> +	size = PAGE_ALIGN(size);
> +	status = efi_call_early(allocate_pages, EFI_ALLOCATE_ANY_PAGES,
> +				EFI_LOADER_DATA, (size >> PAGE_SHIFT), &rom);
>  	if (status != EFI_SUCCESS) {
>  		efi_printk(sys_table, "Failed to alloc mem for rom\n");
>  		return status;
>  
 
Nice catch. The comment could do with a little more information,
including the fact that it's the e820 nosave code that expects
page-aligned ROM regions.

Also, you'll need the same fix for __setup_efi_pci32().