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authorLuiz Capitulino <lcapitulino@redhat.com>2015-05-29 02:20:40 +0300
committerPaolo Bonzini <pbonzini@redhat.com>2015-05-29 15:01:52 +0300
commit0ad83caa21bff9f383c10e73b452425709573042 (patch)
tree03ff130f39628fd94fb67eabaebeebb2929fb5b8 /arch/x86
parent611917258f88fb2fa41d1c2826b193f7c3885b54 (diff)
downloadlinux-0ad83caa21bff9f383c10e73b452425709573042.tar.xz
x86: kvmclock: set scheduler clock stable
If you try to enable NOHZ_FULL on a guest today, you'll get the following error when the guest tries to deactivate the scheduler tick: WARNING: CPU: 3 PID: 2182 at kernel/time/tick-sched.c:192 can_stop_full_tick+0xb9/0x290() NO_HZ FULL will not work with unstable sched clock CPU: 3 PID: 2182 Comm: kworker/3:1 Not tainted 4.0.0-10545-gb9bb6fb #204 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 Workqueue: events flush_to_ldisc ffffffff8162a0c7 ffff88011f583e88 ffffffff814e6ba0 0000000000000002 ffff88011f583ed8 ffff88011f583ec8 ffffffff8104d095 ffff88011f583eb8 0000000000000000 0000000000000003 0000000000000001 0000000000000001 Call Trace: <IRQ> [<ffffffff814e6ba0>] dump_stack+0x4f/0x7b [<ffffffff8104d095>] warn_slowpath_common+0x85/0xc0 [<ffffffff8104d146>] warn_slowpath_fmt+0x46/0x50 [<ffffffff810bd2a9>] can_stop_full_tick+0xb9/0x290 [<ffffffff810bd9ed>] tick_nohz_irq_exit+0x8d/0xb0 [<ffffffff810511c5>] irq_exit+0xc5/0x130 [<ffffffff814f180a>] smp_apic_timer_interrupt+0x4a/0x60 [<ffffffff814eff5e>] apic_timer_interrupt+0x6e/0x80 <EOI> [<ffffffff814ee5d1>] ? _raw_spin_unlock_irqrestore+0x31/0x60 [<ffffffff8108bbc8>] __wake_up+0x48/0x60 [<ffffffff8134836c>] n_tty_receive_buf_common+0x49c/0xba0 [<ffffffff8134a6bf>] ? tty_ldisc_ref+0x1f/0x70 [<ffffffff81348a84>] n_tty_receive_buf2+0x14/0x20 [<ffffffff8134b390>] flush_to_ldisc+0xe0/0x120 [<ffffffff81064d05>] process_one_work+0x1d5/0x540 [<ffffffff81064c81>] ? process_one_work+0x151/0x540 [<ffffffff81065191>] worker_thread+0x121/0x470 [<ffffffff81065070>] ? process_one_work+0x540/0x540 [<ffffffff8106b4df>] kthread+0xef/0x110 [<ffffffff8106b3f0>] ? __kthread_parkme+0xa0/0xa0 [<ffffffff814ef4f2>] ret_from_fork+0x42/0x70 [<ffffffff8106b3f0>] ? __kthread_parkme+0xa0/0xa0 ---[ end trace 06e3507544a38866 ]--- However, it turns out that kvmclock does provide a stable sched_clock callback. So, let the scheduler know this which in turn makes NOHZ_FULL work in the guest. Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kernel/kvmclock.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 42caaef897c8..49487b488061 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -24,6 +24,7 @@
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/memblock.h>
+#include <linux/sched.h>
#include <asm/x86_init.h>
#include <asm/reboot.h>
@@ -217,8 +218,10 @@ static void kvm_shutdown(void)
void __init kvmclock_init(void)
{
+ struct pvclock_vcpu_time_info *vcpu_time;
unsigned long mem;
- int size;
+ int size, cpu;
+ u8 flags;
size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
@@ -264,7 +267,14 @@ void __init kvmclock_init(void)
pv_info.name = "KVM";
if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
- pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
+ pvclock_set_flags(~0);
+
+ cpu = get_cpu();
+ vcpu_time = &hv_clock[cpu].pvti;
+ flags = pvclock_read_flags(vcpu_time);
+ if (flags & PVCLOCK_COUNTS_FROM_ZERO)
+ set_sched_clock_stable();
+ put_cpu();
}
int __init kvm_setup_vsyscall_timeinfo(void)