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

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Date:   Thu, 10 Aug 2017 16:46:37 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Matt Fleming <matt@...eblueprint.co.uk>
Cc:     Stuart Hayes <stuart.w.hayes@...il.com>,
        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


* Matt Fleming <matt@...eblueprint.co.uk> wrote:

> 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().

Just a quick ping: is this fix being worked on?

Thanks,

	Ingo