linux-kernel - Re: [PATCH v2 0/3] x86/efi: Identity mapping pagetable

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Date:	Fri, 05 Oct 2012 14:54:51 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Matt Fleming" <matt@...sole-pimps.org>
Cc:	"Matt Fleming" <matt.fleming@...el.com>,
	"Ingo Molnar" <mingo@...nel.org>, <x86@...nel.org>,
	"Matthew Garrett" <mjg@...hat.com>, <linux-efi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 0/3] x86/efi: Identity mapping pagetable

>>> On 05.10.12 at 15:14, Matt Fleming <matt@...sole-pimps.org> wrote:
> From: Matt Fleming <matt.fleming@...el.com>
> 
> This series upgrades real_mode_header->trampoline_pgd to a proper
> kernel pagetable instead of just mapping the kernel text and module
> space. It also inserts the physical mappings for anything we
> ioremap(), so I/O regions are always accessible via their physical
> addresses whenever this pagetable is loaded, making it a true identity
> mapping.
> 
> These changes make it suitable for loading when calling virtual EFI
> runtime functions on x86-64. The main benefit of this change is to fix
> the ASUS firmware bug documented here,
> 
> 	 https://lkml.org/lkml/2012/8/7/108 
> 
> but having our own EFI pagetable makes sense anyway. The memory map
> code is easily the most complicatd part of the EFI infrastructure, and
> it's likely that there will be other funky stuff we have to do with
> our memory map as more and more machines ship with various
> implementations of EFI firmware.
> 
> Note that we only switch to the identity pagetable for x86-64. I'm
> unaware of any bugs like the above on 32-bit EFI platforms, but we can
> easily adopt the 64-bit scheme if one is discovered.
> 
> v2: Based on feedback from Jan Beulich delete the 32-bit changes in
> [PATCH 1/3], they were likely to create more problems than they would
> solve and the identity I/O mappings are unused on 32-bit anyway.
> 
> Matt Fleming (2):
>   x86, mm: Include the entire kernel memory map in trampoline_pgd
>   x86, efi: 1:1 pagetable mapping for virtual EFI calls

Acked-by: Jan Beulich <jbeulich@...e.com>

(I know too little about the tboot code to meaningfully ack that
one too.)

> Xiaoyan Zhang (1):
>   x86/kernel: remove tboot 1:1 page table creation code
> 
>  arch/x86/include/asm/efi.h     |  28 ++++++++---
>  arch/x86/kernel/tboot.c        |  78 ++----------------------------
>  arch/x86/mm/init_64.c          |   9 +++-
>  arch/x86/mm/ioremap.c          | 105 +++++++++++++++++++++++++++++++++++++++++
>  arch/x86/platform/efi/efi_64.c |  15 ++++++
>  arch/x86/realmode/init.c       |  17 ++++++-
>  6 files changed, 169 insertions(+), 83 deletions(-)
> 
> -- 
> 1.7.11.4



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