[PATCH 11/12] kexec: allow architectures to override boot mapping

[Russell King - ARM Linux]

On Fri, Apr 29, 2016 at 08:44:29PM +0530, Pratyush Anand wrote:
> On Thu, Apr 28, 2016 at 2:58 PM, Russell King
> <rmk+kernel at arm.linux.org.uk> wrote:
> > kexec physical addresses are the boot-time view of the system.  For
> > certain ARM systems (such as Keystone 2), the boot view of the system
> > does not match the kernel's view of the system: the boot view uses a
> > special alias in the lower 4GB of the physical address space.
> >
> > To cater for these kinds of setups, we need to translate between the
> > boot view physical addresses and the normal kernel view physical
> > addresses.  This patch extracts the current transation points into
> > linux/kexec.h, and allows an architecture to override the functions.
> >
> > Due to the translations required, we unfortunately end up with six
> > translation functions, which are reduced down to four that the
> > architecture can override.
> >
> > Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
> 
> I must be missing something when I am thinking that, had we passed
> arch_phys_to_idmap_offset to user space, this patch would not have
> been needed, and things would have been more simpler. Please help me
> to understand why passing arch_phys_to_idmap_offset to user space
> would not be a good idea.

Sorry, I disagree.

Even if we thought that passing the offset to userspace would be a
good idea, it does nothing to solve each site in this patch.  This
patch would still be necessary.

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