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| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2017-09-12 16:37:33 +0200 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2018-10-09 11:20:57 +0200 |
| commit | ce3dc447493ff4186b192b38d723ab5e8c1eb52f (patch) | |
| tree | f93f58afcd85087876a1ab9badcdaed76b5a37fe /arch/s390/kernel/machine_kexec.c | |
| parent | ff340d2472ec7618443913928af9fb85a7009270 (diff) | |
| download | linux-ce3dc447493ff4186b192b38d723ab5e8c1eb52f.tar.gz linux-ce3dc447493ff4186b192b38d723ab5e8c1eb52f.tar.bz2 linux-ce3dc447493ff4186b192b38d723ab5e8c1eb52f.zip | |
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 <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/machine_kexec.c')
| -rw-r--r-- | arch/s390/kernel/machine_kexec.c | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c index b7020e721ae3..cb582649aba6 100644 --- a/arch/s390/kernel/machine_kexec.c +++ b/arch/s390/kernel/machine_kexec.c @@ -142,18 +142,27 @@ static noinline void __machine_kdump(void *image) } #endif +static unsigned long do_start_kdump(unsigned long addr) +{ + struct kimage *image = (struct kimage *) addr; + int (*start_kdump)(int) = (void *)image->start; + int rc; + + __arch_local_irq_stnsm(0xfb); /* disable DAT */ + rc = start_kdump(0); + __arch_local_irq_stosm(0x04); /* enable DAT */ + return rc; +} + /* * Check if kdump checksums are valid: We call purgatory with parameter "0" */ static bool kdump_csum_valid(struct kimage *image) { #ifdef CONFIG_CRASH_DUMP - int (*start_kdump)(int) = (void *)image->start; int rc; - __arch_local_irq_stnsm(0xfb); /* disable DAT */ - rc = start_kdump(0); - __arch_local_irq_stosm(0x04); /* enable DAT */ + rc = CALL_ON_STACK(do_start_kdump, S390_lowcore.nodat_stack, 1, image); return rc == 0; #else return false; |