x86: kvm: Revert "remove sched notifier for cross-cpu migrations"

The following point:

    2. per-CPU pvclock time info is updated if the
       underlying CPU changes.

Is not true anymore since "KVM: x86: update pvclock area conditionally,
on cpu migration".

Add task migration notification back.

Problem noticed by Andy Lutomirski.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
CC: stable@kernel.org # 3.11+
This commit is contained in:
Marcelo Tosatti 2015-03-23 20:21:51 -03:00
parent 58d2930f4e
commit 0a4e6be9ca
5 changed files with 76 additions and 8 deletions

View File

@ -95,6 +95,7 @@ unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
struct pvclock_vsyscall_time_info {
struct pvclock_vcpu_time_info pvti;
u32 migrate_count;
} __attribute__((__aligned__(SMP_CACHE_BYTES)));
#define PVTI_SIZE sizeof(struct pvclock_vsyscall_time_info)

View File

@ -141,7 +141,46 @@ void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
}
static struct pvclock_vsyscall_time_info *pvclock_vdso_info;
static struct pvclock_vsyscall_time_info *
pvclock_get_vsyscall_user_time_info(int cpu)
{
if (!pvclock_vdso_info) {
BUG();
return NULL;
}
return &pvclock_vdso_info[cpu];
}
struct pvclock_vcpu_time_info *pvclock_get_vsyscall_time_info(int cpu)
{
return &pvclock_get_vsyscall_user_time_info(cpu)->pvti;
}
#ifdef CONFIG_X86_64
static int pvclock_task_migrate(struct notifier_block *nb, unsigned long l,
void *v)
{
struct task_migration_notifier *mn = v;
struct pvclock_vsyscall_time_info *pvti;
pvti = pvclock_get_vsyscall_user_time_info(mn->from_cpu);
/* this is NULL when pvclock vsyscall is not initialized */
if (unlikely(pvti == NULL))
return NOTIFY_DONE;
pvti->migrate_count++;
return NOTIFY_DONE;
}
static struct notifier_block pvclock_migrate = {
.notifier_call = pvclock_task_migrate,
};
/*
* Initialize the generic pvclock vsyscall state. This will allocate
* a/some page(s) for the per-vcpu pvclock information, set up a
@ -155,12 +194,17 @@ int __init pvclock_init_vsyscall(struct pvclock_vsyscall_time_info *i,
WARN_ON (size != PVCLOCK_VSYSCALL_NR_PAGES*PAGE_SIZE);
pvclock_vdso_info = i;
for (idx = 0; idx <= (PVCLOCK_FIXMAP_END-PVCLOCK_FIXMAP_BEGIN); idx++) {
__set_fixmap(PVCLOCK_FIXMAP_BEGIN + idx,
__pa(i) + (idx*PAGE_SIZE),
PAGE_KERNEL_VVAR);
}
register_task_migration_notifier(&pvclock_migrate);
return 0;
}
#endif

View File

@ -82,18 +82,15 @@ static notrace cycle_t vread_pvclock(int *mode)
cycle_t ret;
u64 last;
u32 version;
u32 migrate_count;
u8 flags;
unsigned cpu, cpu1;
/*
* Note: hypervisor must guarantee that:
* 1. cpu ID number maps 1:1 to per-CPU pvclock time info.
* 2. that per-CPU pvclock time info is updated if the
* underlying CPU changes.
* 3. that version is increased whenever underlying CPU
* changes.
*
* When looping to get a consistent (time-info, tsc) pair, we
* also need to deal with the possibility we can switch vcpus,
* so make sure we always re-fetch time-info for the current vcpu.
*/
do {
cpu = __getcpu() & VGETCPU_CPU_MASK;
@ -104,6 +101,8 @@ static notrace cycle_t vread_pvclock(int *mode)
pvti = get_pvti(cpu);
migrate_count = pvti->migrate_count;
version = __pvclock_read_cycles(&pvti->pvti, &ret, &flags);
/*
@ -115,7 +114,8 @@ static notrace cycle_t vread_pvclock(int *mode)
cpu1 = __getcpu() & VGETCPU_CPU_MASK;
} while (unlikely(cpu != cpu1 ||
(pvti->pvti.version & 1) ||
pvti->pvti.version != version));
pvti->pvti.version != version ||
pvti->migrate_count != migrate_count));
if (unlikely(!(flags & PVCLOCK_TSC_STABLE_BIT)))
*mode = VCLOCK_NONE;

View File

@ -176,6 +176,14 @@ extern void get_iowait_load(unsigned long *nr_waiters, unsigned long *load);
extern void calc_global_load(unsigned long ticks);
extern void update_cpu_load_nohz(void);
/* Notifier for when a task gets migrated to a new CPU */
struct task_migration_notifier {
struct task_struct *task;
int from_cpu;
int to_cpu;
};
extern void register_task_migration_notifier(struct notifier_block *n);
extern unsigned long get_parent_ip(unsigned long addr);
extern void dump_cpu_task(int cpu);

View File

@ -996,6 +996,13 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
rq_clock_skip_update(rq, true);
}
static ATOMIC_NOTIFIER_HEAD(task_migration_notifier);
void register_task_migration_notifier(struct notifier_block *n)
{
atomic_notifier_chain_register(&task_migration_notifier, n);
}
#ifdef CONFIG_SMP
void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
{
@ -1026,10 +1033,18 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
trace_sched_migrate_task(p, new_cpu);
if (task_cpu(p) != new_cpu) {
struct task_migration_notifier tmn;
if (p->sched_class->migrate_task_rq)
p->sched_class->migrate_task_rq(p, new_cpu);
p->se.nr_migrations++;
perf_sw_event_sched(PERF_COUNT_SW_CPU_MIGRATIONS, 1, 0);
tmn.task = p;
tmn.from_cpu = task_cpu(p);
tmn.to_cpu = new_cpu;
atomic_notifier_call_chain(&task_migration_notifier, 0, &tmn);
}
__set_task_cpu(p, new_cpu);