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| author | Christian Borntraeger <borntraeger@linux.ibm.com> | 2022-05-30 12:27:05 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-06-14 19:45:15 +0300 |
| commit | bc748d55ae36c0d28ea788e711e9cff5f2168722 (patch) | |
| tree | 1045bf988630ed0613819d9cf66733fb4f6bb602 | |
| parent | dfa95e7ffdb415b061bef6e29e687b21e26f1c34 (diff) | |
| download | linux-bc748d55ae36c0d28ea788e711e9cff5f2168722.tar.xz | |
s390/gmap: voluntarily schedule during key setting
[ Upstream commit 6d5946274df1fff539a7eece458a43be733d1db8 ]
With large and many guest with storage keys it is possible to create
large latencies or stalls during initial key setting:
rcu: INFO: rcu_sched self-detected stall on CPU
rcu: 18-....: (2099 ticks this GP) idle=54e/1/0x4000000000000002 softirq=35598716/35598716 fqs=998
(t=2100 jiffies g=155867385 q=20879)
Task dump for CPU 18:
CPU 1/KVM R running task 0 1030947 256019 0x06000004
Call Trace:
sched_show_task
rcu_dump_cpu_stacks
rcu_sched_clock_irq
update_process_times
tick_sched_handle
tick_sched_timer
__hrtimer_run_queues
hrtimer_interrupt
do_IRQ
ext_int_handler
ptep_zap_key
The mmap lock is held during the page walking but since this is a
semaphore scheduling is still possible. Same for the kvm srcu.
To minimize overhead do this on every segment table entry or large page.
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Link: https://lore.kernel.org/r/20220530092706.11637-2-borntraeger@linux.ibm.com
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | arch/s390/mm/gmap.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c index 1ac73917a8d3..b8ae4a4aa2ba 100644 --- a/arch/s390/mm/gmap.c +++ b/arch/s390/mm/gmap.c @@ -2608,6 +2608,18 @@ static int __s390_enable_skey_pte(pte_t *pte, unsigned long addr, return 0; } +/* + * Give a chance to schedule after setting a key to 256 pages. + * We only hold the mm lock, which is a rwsem and the kvm srcu. + * Both can sleep. + */ +static int __s390_enable_skey_pmd(pmd_t *pmd, unsigned long addr, + unsigned long next, struct mm_walk *walk) +{ + cond_resched(); + return 0; +} + static int __s390_enable_skey_hugetlb(pte_t *pte, unsigned long addr, unsigned long hmask, unsigned long next, struct mm_walk *walk) @@ -2630,12 +2642,14 @@ static int __s390_enable_skey_hugetlb(pte_t *pte, unsigned long addr, end = start + HPAGE_SIZE - 1; __storage_key_init_range(start, end); set_bit(PG_arch_1, &page->flags); + cond_resched(); return 0; } static const struct mm_walk_ops enable_skey_walk_ops = { .hugetlb_entry = __s390_enable_skey_hugetlb, .pte_entry = __s390_enable_skey_pte, + .pmd_entry = __s390_enable_skey_pmd, }; int s390_enable_skey(void) |