diff options
| author | Luiz Capitulino <lcapitulino@redhat.com> | 2015-05-28 20:20:40 -0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2015-05-29 14:01:52 +0200 |
| commit | 0ad83caa21bff9f383c10e73b452425709573042 (patch) | |
| tree | 03ff130f39628fd94fb67eabaebeebb2929fb5b8 /arch | |
| parent | 611917258f88fb2fa41d1c2826b193f7c3885b54 (diff) | |
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')
| -rw-r--r-- | arch/x86/kernel/kvmclock.c | 14 |
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) |