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xen: add steal_clock support on x86

The pv_time_ops structure contains a function pointer for the
"steal_clock" functionality used only by KVM and Xen on ARM. Xen on x86
uses its own mechanism to account for the "stolen" time a thread wasn't
able to run due to hypervisor scheduling.

Add support in Xen arch independent time handling for this feature by
moving it out of the arm arch into drivers/xen and remove the x86 Xen
hack.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
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jgross1 authored and David Vrabel committed May 20, 2016
1 parent c7ebf9d commit ecb23dc6f2eff0ce64dd60351a81f376f13b12cc
Showing with 25 additions and 69 deletions.
  1. +2 −16 arch/arm/xen/enlighten.c
  2. +2 −42 arch/x86/xen/time.c
  3. +20 −0 drivers/xen/time.c
  4. +0 −1 include/linux/kernel_stat.h
  5. +1 −0 include/xen/xen-ops.h
  6. +0 −10 kernel/sched/cputime.c
@@ -12,7 +12,6 @@
#include <xen/page.h>
#include <xen/interface/sched.h>
#include <xen/xen-ops.h>
#include <asm/paravirt.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/xen-ops.h>
@@ -86,19 +85,6 @@ int xen_unmap_domain_gfn_range(struct vm_area_struct *vma,
}
EXPORT_SYMBOL_GPL(xen_unmap_domain_gfn_range);
static unsigned long long xen_stolen_accounting(int cpu)
{
struct vcpu_runstate_info state;
BUG_ON(cpu != smp_processor_id());
xen_get_runstate_snapshot(&state);
WARN_ON(state.state != RUNSTATE_running);
return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
}
static void xen_read_wallclock(struct timespec64 *ts)
{
u32 version;
@@ -432,8 +418,8 @@ static int __init xen_guest_init(void)
register_cpu_notifier(&xen_cpu_notifier);
pv_time_ops.steal_clock = xen_stolen_accounting;
static_key_slow_inc(&paravirt_steal_enabled);
xen_time_setup_guest();
if (xen_initial_domain())
pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
@@ -11,8 +11,6 @@
#include <linux/interrupt.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/kernel_stat.h>
#include <linux/math64.h>
#include <linux/gfp.h>
#include <linux/slab.h>
#include <linux/pvclock_gtod.h>
@@ -31,44 +29,6 @@
/* Xen may fire a timer up to this many ns early */
#define TIMER_SLOP 100000
#define NS_PER_TICK (1000000000LL / HZ)
/* snapshots of runstate info */
static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate_snapshot);
/* unused ns of stolen time */
static DEFINE_PER_CPU(u64, xen_residual_stolen);
static void do_stolen_accounting(void)
{
struct vcpu_runstate_info state;
struct vcpu_runstate_info *snap;
s64 runnable, offline, stolen;
cputime_t ticks;
xen_get_runstate_snapshot(&state);
WARN_ON(state.state != RUNSTATE_running);
snap = this_cpu_ptr(&xen_runstate_snapshot);
/* work out how much time the VCPU has not been runn*ing* */
runnable = state.time[RUNSTATE_runnable] - snap->time[RUNSTATE_runnable];
offline = state.time[RUNSTATE_offline] - snap->time[RUNSTATE_offline];
*snap = state;
/* Add the appropriate number of ticks of stolen time,
including any left-overs from last time. */
stolen = runnable + offline + __this_cpu_read(xen_residual_stolen);
if (stolen < 0)
stolen = 0;
ticks = iter_div_u64_rem(stolen, NS_PER_TICK, &stolen);
__this_cpu_write(xen_residual_stolen, stolen);
account_steal_ticks(ticks);
}
/* Get the TSC speed from Xen */
static unsigned long xen_tsc_khz(void)
@@ -335,8 +295,6 @@ static irqreturn_t xen_timer_interrupt(int irq, void *dev_id)
ret = IRQ_HANDLED;
}
do_stolen_accounting();
return ret;
}
@@ -431,6 +389,8 @@ static void __init xen_time_init(void)
xen_setup_timer(cpu);
xen_setup_cpu_clockevents();
xen_time_setup_guest();
if (xen_initial_domain())
pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
}
@@ -6,6 +6,7 @@
#include <linux/math64.h>
#include <linux/gfp.h>
#include <asm/paravirt.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>
@@ -75,6 +76,15 @@ bool xen_vcpu_stolen(int vcpu)
return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
}
static u64 xen_steal_clock(int cpu)
{
struct vcpu_runstate_info state;
BUG_ON(cpu != smp_processor_id());
xen_get_runstate_snapshot(&state);
return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
}
void xen_setup_runstate_info(int cpu)
{
struct vcpu_register_runstate_memory_area area;
@@ -86,3 +96,13 @@ void xen_setup_runstate_info(int cpu)
BUG();
}
void __init xen_time_setup_guest(void)
{
pv_time_ops.steal_clock = xen_steal_clock;
static_key_slow_inc(&paravirt_steal_enabled);
/*
* We can't set paravirt_steal_rq_enabled as this would require the
* capability to read another cpu's runstate info.
*/
}
@@ -92,7 +92,6 @@ static inline void account_process_tick(struct task_struct *tsk, int user)
extern void account_process_tick(struct task_struct *, int user);
#endif
extern void account_steal_ticks(unsigned long ticks);
extern void account_idle_ticks(unsigned long ticks);
#endif /* _LINUX_KERNEL_STAT_H */
@@ -21,6 +21,7 @@ void xen_resume_notifier_unregister(struct notifier_block *nb);
bool xen_vcpu_stolen(int vcpu);
void xen_setup_runstate_info(int cpu);
void xen_time_setup_guest(void);
void xen_get_runstate_snapshot(struct vcpu_runstate_info *res);
int xen_setup_shutdown_event(void);
@@ -489,16 +489,6 @@ void account_process_tick(struct task_struct *p, int user_tick)
account_idle_time(cputime_one_jiffy);
}
/*
* Account multiple ticks of steal time.
* @p: the process from which the cpu time has been stolen
* @ticks: number of stolen ticks
*/
void account_steal_ticks(unsigned long ticks)
{
account_steal_time(jiffies_to_cputime(ticks));
}
/*
* Account multiple ticks of idle time.
* @ticks: number of stolen ticks

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