linux-kernel - Re: [PATCHv3] x86: EFI stub support for large memory maps

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Date:	Wed, 25 Sep 2013 16:45:41 -0600
From:	Linn Crosetto <linn@...com>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	matt.fleming@...el.com, hpa@...or.com, tglx@...utronix.de,
	mingo@...hat.com, x86@...nel.org, yinghai@...nel.org,
	linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3] x86: EFI stub support for large memory maps

On Wed, Sep 25, 2013 at 01:58:40PM +0100, Matt Fleming wrote:
> On Sun, 22 Sep, at 07:59:08PM, Linn Crosetto wrote:
> > This patch fixes a problem with EFI memory maps larger than 128 entries
> > when booting using the EFI stub, which results in overflowing e820_map
> > in boot_params and an eventual halt when checking the map size in
> > sanitize_e820_map().
> > 
> > If the number of map entries is greater than what can fit in e820_map,
> > add the extra entries to the setup_data list using type SETUP_E820_EXT.
> > These extra entries are then picked up when the setup_data list is
> > parsed in parse_e820_ext().
> > 
> > Signed-off-by: Linn Crosetto <linn@...com>
> > ---
> > Changes from v2:
> >  * Removed unnecessary optimization in alloc_e820ext() (Matt Fleming)
> >  * Fixed a bug where an incorrect buffer size may be passed to
> >    get_memory_map when jumping to get_map
> > 
> >  arch/x86/boot/compressed/eboot.c | 239 +++++++++++++++++++++++++++------------
> >  1 file changed, 167 insertions(+), 72 deletions(-)
> 
> Thanks Linn. I applied this to the 'next' branch at,
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/mfleming/efi.git
> 
> but it required a bit of massaging to apply on top of the changes
> already there. Could you confirm that my changes are OK? I've included
> the modified commit below.

I have tested the 'next' branch on a system with a large number of entries in
the memory map and the merge appears to be functionally correct. 

With the change in commit ae8e9060, I noticed the memory map is no longer placed
in memory allocated with low_alloc(). I have not looked into what effect it
could have, if any.

> +	/* Historic? */
> +	boot_params->alt_mem_k = 32 * 1024;
> +
> +	status = setup_e820(boot_params, e820ext, e820ext_size);
>  
>  	return EFI_SUCCESS;

I might add the following to your merge for semantic reasons:

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 04b228d..a7677ba 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -730,6 +730,8 @@ get_map:
        boot_params->alt_mem_k = 32 * 1024;
 
        status = setup_e820(boot_params, e820ext, e820ext_size);
+       if (status != EFI_SUCCESS)
+               return status;
 
        return EFI_SUCCESS;


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