[PATCH v2 4/6] ARM: idmap: use idmap_pgd when setting up mm for reboot

[Will Deacon]

On Wed, Nov 30, 2011 at 11:31:13AM +0000, Catalin Marinas wrote:
> On 28 November 2011 18:28, Will Deacon <will.deacon at arm.com> wrote:
> > For soft-rebooting a system, it is necessary to map the MMU-off code
> > with an identity mapping so that execution can continue safely once the
> > MMU has been switched off.
> >
> > Currently, switch_mm_for_reboot takes out a 1:1 mapping from 0x0 to
> > TASK_SIZE during reboot in the hope that the reset code lives at a
> > physical address corresponding to a userspace virtual address.
> >
> > This patch modifies the code so that we switch to the idmap_pgd tables,
> > which contain a 1:1 mapping of the cpu_reset code. This has the
> > advantage of only remapping the code that we need and also means we
> > don't need to worry about allocating a pgd from an atomic context in the
> > case that the physical address of the cpu_reset code aliases with the
> > virtual space used by the kernel.
> >
> > Acked-by: Dave Martin <dave.martin at linaro.org>
> > Signed-off-by: Will Deacon <will.deacon at arm.com>
> 
> Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>

Thanks Catalin.

Russell - could you have a quick look at these please as the changes to
setup_mm_for_reboot are required for the LPAE stuff?

Cheers,

Will