[PATCH] ARM: mm: ensure TTBR0 is restored when changing ASID on rollover

On 7 June 2011 11:38, Will Deacon [off-list ref] wrote:

In 52af9c6c ("ARM: 6943/1: mm: use TTBR1 instead of reserved context ID")
I updated the ASID rollover code to use only the kernel page tables
whilst updating the ASID.

Unfortunately, the code to restore the user page tables was part of a
later patch which isn't yet in mainline, so this leaves the code
quite broken.

IOW, after an ASID roll-over on SMP, the cross-called reset_context()
function sets TTBR0 to swapper_pg_dir but never sets it back to the
one of the currently running process. So interrupted user space
processes would fault when returning from an ASID roll-over event
happening on a different CPU.

This patch fixes the issue by calling cpu_switch_mm to change the ASID
which has the side-effect of setting up TTBR0 to point to the user
tables.

Reported-by: Marc Zyngier <redacted>
Signed-off-by: Will Deacon <redacted>

Acked-by: Catalin Marinas <catalin.marinas@arm.com>