linux-kernel - Re: [PATCH] x86/mm/pageattr: Use _PAGE_GLOBAL bit for EFI page table mappings

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Date:	Fri, 29 Jan 2016 16:25:29 +0000
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
Cc:	linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ricardo Neri <ricardo.neri@...el.com>,
	Ravi Shankar <ravi.v.shankar@...el.com>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86/mm/pageattr: Use _PAGE_GLOBAL bit for EFI page table
 mappings

On Wed, 27 Jan, at 10:34:56AM, Sai Praneeth Prakhya wrote:
> From: Sai Praneeth <sai.praneeth.prakhya@...el.com>
> 
> Since EFI page tables can be treated as kernel page tables they should
> be global. All the other page mapping functions in pageattr.c set the
> _PAGE_GLOBAL bit and we want to avoid inconsistencies when we map a page
> in the EFI code paths, for example when that page is split in
> __split_large_page(), etc. It also makes it easier to validate that the
> EFI region mappings have the correct attributes because there are fewer
> differences compared with regular kernel mappings.
> 
> Cc: Ricardo Neri <ricardo.neri@...el.com>
> Cc: Ravi Shankar <ravi.v.shankar@...el.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Matt Fleming <matt@...eblueprint.co.uk>
> Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
> ---
>  arch/x86/mm/pageattr.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)

Reducing any differences between the EFI mapping and regular kernel
mapping code in pageattr.c is a plus.

Thanks Sai, applied.