]> git.baikalelectronics.ru Git - kernel.git/commit
arm64: kpti: Add ->enable callback to remap swapper using nG mappings
authorWill Deacon <will.deacon@arm.com>
Tue, 6 Feb 2018 22:22:50 +0000 (22:22 +0000)
committerCatalin Marinas <catalin.marinas@arm.com>
Tue, 6 Feb 2018 22:53:18 +0000 (22:53 +0000)
commita43780ec22ac6a1c11751d15ddf7a53bcab792ce
treea92a073173ecf55d39c39eb6a1ed3ec4f55ff11d
parentea6c504f69ae259d75d133e50dbbbf5705586d08
arm64: kpti: Add ->enable callback to remap swapper using nG mappings

Defaulting to global mappings for kernel space is generally good for
performance and appears to be necessary for Cavium ThunderX. If we
subsequently decide that we need to enable kpti, then we need to rewrite
our existing page table entries to be non-global. This is fiddly, and
made worse by the possible use of contiguous mappings, which require
a strict break-before-make sequence.

Since the enable callback runs on each online CPU from stop_machine
context, we can have all CPUs enter the idmap, where secondaries can
wait for the primary CPU to rewrite swapper with its MMU off. It's all
fairly horrible, but at least it only runs once.

Tested-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
arch/arm64/include/asm/assembler.h
arch/arm64/kernel/cpufeature.c
arch/arm64/mm/proc.S