From ce3dc447493ff4186b192b38d723ab5e8c1eb52f Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Tue, 12 Sep 2017 16:37:33 +0200 Subject: s390: add support for virtually mapped kernel stacks With virtually mapped kernel stacks the kernel stack overflow detection is now fault based, every stack has a guard page in the vmalloc space. The panic_stack is renamed to nodat_stack and is used for all function that need to run without DAT, e.g. memcpy_real or do_start_kdump. The main effect is a reduction in the kernel image size as with vmap stacks the old style overflow checking that adds two instructions per function is not needed anymore. Result from bloat-o-meter: add/remove: 20/1 grow/shrink: 13/26854 up/down: 2198/-216240 (-214042) In regard to performance the micro-benchmark for fork has a hit of a few microseconds, allocating 4 pages in vmalloc space is more expensive compare to an order-2 page allocation. But with real workload I could not find a noticeable difference. Acked-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/entry.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch/s390/kernel/entry.h') diff --git a/arch/s390/kernel/entry.h b/arch/s390/kernel/entry.h index 472fa2f1a4a5..c3816ae108b0 100644 --- a/arch/s390/kernel/entry.h +++ b/arch/s390/kernel/entry.h @@ -86,4 +86,7 @@ DECLARE_PER_CPU(u64, mt_cycles[8]); void gs_load_bc_cb(struct pt_regs *regs); void set_fs_fixup(void); +unsigned long stack_alloc(void); +void stack_free(unsigned long stack); + #endif /* _ENTRY_H */ -- cgit v1.2.3