Re: [PATCH v4 1/4] xen: move xen_setup_runstate_info and get_runstate_snapshot to drivers/xen/time.c

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Tue, May 28, 2013 at 06:54:29PM +0100, Stefano Stabellini wrote:
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> Acked-by: Ian Campbell <ian.campbell@citrix.com>
> CC: konrad.wilk@oracle.com
> 
> Changes in v2:
> - leave do_stolen_accounting in arch/x86/xen/time.c;
> - use the new common functions in arch/ia64/xen/time.c.

So you also modify the function.

> ---
>  arch/ia64/xen/time.c  |   48 +++----------------------
>  arch/x86/xen/time.c   |   76 +----------------------------------------
>  drivers/xen/Makefile  |    2 +-
>  drivers/xen/time.c    |   91 +++++++++++++++++++++++++++++++++++++++++++++++++
>  include/xen/xen-ops.h |    5 +++
>  5 files changed, 104 insertions(+), 118 deletions(-)
>  create mode 100644 drivers/xen/time.c
> 
> diff --git a/arch/ia64/xen/time.c b/arch/ia64/xen/time.c
> index 1f8244a..79a0b8c 100644
> --- a/arch/ia64/xen/time.c
> +++ b/arch/ia64/xen/time.c
> @@ -34,53 +34,17 @@
>  
>  #include "../kernel/fsyscall_gtod_data.h"
>  
> -static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
>  static DEFINE_PER_CPU(unsigned long, xen_stolen_time);
>  static DEFINE_PER_CPU(unsigned long, xen_blocked_time);
>  
>  /* taken from i386/kernel/time-xen.c */
>  static void xen_init_missing_ticks_accounting(int cpu)
>  {
> -	struct vcpu_register_runstate_memory_area area;
> -	struct vcpu_runstate_info *runstate = &per_cpu(xen_runstate, cpu);
> -	int rc;
> +	xen_setup_runstate_info(&runstate);
>  
> -	memset(runstate, 0, sizeof(*runstate));
> -
> -	area.addr.v = runstate;
> -	rc = HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area, cpu,
> -				&area);
> -	WARN_ON(rc && rc != -ENOSYS);
> -
> -	per_cpu(xen_blocked_time, cpu) = runstate->time[RUNSTATE_blocked];
> -	per_cpu(xen_stolen_time, cpu) = runstate->time[RUNSTATE_runnable]
> -					    + runstate->time[RUNSTATE_offline];
> -}
> -
> -/*
> - * Runstate accounting
> - */
> -/* stolen from arch/x86/xen/time.c */
> -static void get_runstate_snapshot(struct vcpu_runstate_info *res)
> -{
> -	u64 state_time;
> -	struct vcpu_runstate_info *state;
> -
> -	BUG_ON(preemptible());
> -
> -	state = &__get_cpu_var(xen_runstate);
> -
> -	/*
> -	 * The runstate info is always updated by the hypervisor on
> -	 * the current CPU, so there's no need to use anything
> -	 * stronger than a compiler barrier when fetching it.
> -	 */
> -	do {
> -		state_time = state->state_entry_time;
> -		rmb();
> -		*res = *state;
> -		rmb();
> -	} while (state->state_entry_time != state_time);
> +	per_cpu(xen_blocked_time, cpu) = runstate.time[RUNSTATE_blocked];
> +	per_cpu(xen_stolen_time, cpu) = runstate.time[RUNSTATE_runnable]
> +					    + runstate.time[RUNSTATE_offline];
>  }
>  
>  #define NS_PER_TICK (1000000000LL/HZ)
> @@ -94,7 +58,7 @@ consider_steal_time(unsigned long new_itm)
>  	struct vcpu_runstate_info runstate;
>  	struct task_struct *p = current;
>  
> -	get_runstate_snapshot(&runstate);
> +	xen_get_runstate_snapshot(&runstate);
>  
>  	/*
>  	 * Check for vcpu migration effect
> @@ -202,7 +166,7 @@ static unsigned long long xen_sched_clock(void)
>  	 */
>  	now = ia64_native_sched_clock();
>  
> -	get_runstate_snapshot(&runstate);
> +	xen_get_runstate_snapshot(&runstate);
>  
>  	WARN_ON(runstate.state != RUNSTATE_running);
>  
> diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
> index 3d88bfd..c0ca15e 100644
> --- a/arch/x86/xen/time.c
> +++ b/arch/x86/xen/time.c
> @@ -30,9 +30,6 @@
>  #define TIMER_SLOP	100000
>  #define NS_PER_TICK	(1000000000LL / HZ)
>  
> -/* runstate info updated by Xen */
> -static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
> -
>  /* snapshots of runstate info */
>  static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate_snapshot);
>  
> @@ -40,77 +37,6 @@ static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate_snapshot);
>  static DEFINE_PER_CPU(u64, xen_residual_stolen);
>  static DEFINE_PER_CPU(u64, xen_residual_blocked);
>  
> -/* return an consistent snapshot of 64-bit time/counter value */
> -static u64 get64(const u64 *p)
> -{
> -	u64 ret;
> -
> -	if (BITS_PER_LONG < 64) {
> -		u32 *p32 = (u32 *)p;
> -		u32 h, l;
> -
> -		/*
> -		 * Read high then low, and then make sure high is
> -		 * still the same; this will only loop if low wraps
> -		 * and carries into high.
> -		 * XXX some clean way to make this endian-proof?
> -		 */
> -		do {
> -			h = p32[1];
> -			barrier();
> -			l = p32[0];
> -			barrier();
> -		} while (p32[1] != h);
> -
> -		ret = (((u64)h) << 32) | l;
> -	} else
> -		ret = *p;
> -
> -	return ret;
> -}
> -
> -/*
> - * Runstate accounting
> - */
> -static void get_runstate_snapshot(struct vcpu_runstate_info *res)
> -{
> -	u64 state_time;
> -	struct vcpu_runstate_info *state;
> -
> -	BUG_ON(preemptible());
> -
> -	state = &__get_cpu_var(xen_runstate);
> -
> -	/*
> -	 * The runstate info is always updated by the hypervisor on
> -	 * the current CPU, so there's no need to use anything
> -	 * stronger than a compiler barrier when fetching it.
> -	 */
> -	do {
> -		state_time = get64(&state->state_entry_time);
> -		barrier();
> -		*res = *state;
> -		barrier();
> -	} while (get64(&state->state_entry_time) != state_time);
> -}
> -
> -/* return true when a vcpu could run but has no real cpu to run on */
> -bool xen_vcpu_stolen(int vcpu)
> -{
> -	return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
> -}
> -
> -void xen_setup_runstate_info(int cpu)
> -{
> -	struct vcpu_register_runstate_memory_area area;
> -
> -	area.addr.v = &per_cpu(xen_runstate, cpu);
> -
> -	if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area,
> -			       cpu, &area))
> -		BUG();
> -}
> -
>  static void do_stolen_accounting(void)
>  {
>  	struct vcpu_runstate_info state;
> @@ -118,7 +44,7 @@ static void do_stolen_accounting(void)
>  	s64 blocked, runnable, offline, stolen;
>  	cputime_t ticks;
>  
> -	get_runstate_snapshot(&state);
> +	xen_get_runstate_snapshot(&state);
>  
>  	WARN_ON(state.state != RUNSTATE_running);
>  
> diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
> index eabd0ee..2bf461a 100644
> --- a/drivers/xen/Makefile
> +++ b/drivers/xen/Makefile
> @@ -3,7 +3,7 @@ obj-y	+= manage.o
>  obj-$(CONFIG_HOTPLUG_CPU)		+= cpu_hotplug.o
>  endif
>  obj-$(CONFIG_X86)			+= fallback.o
> -obj-y	+= grant-table.o features.o events.o balloon.o
> +obj-y	+= grant-table.o features.o events.o balloon.o time.o
>  obj-y	+= xenbus/
>  
>  nostackp := $(call cc-option, -fno-stack-protector)
> diff --git a/drivers/xen/time.c b/drivers/xen/time.c
> new file mode 100644
> index 0000000..c2e39d3
> --- /dev/null
> +++ b/drivers/xen/time.c
> @@ -0,0 +1,91 @@
> +/*
> + * Xen stolen ticks accounting.
> + */
> +#include <linux/kernel.h>
> +#include <linux/kernel_stat.h>
> +#include <linux/math64.h>
> +#include <linux/gfp.h>
> +
> +#include <asm/xen/hypervisor.h>
> +#include <asm/xen/hypercall.h>
> +
> +#include <xen/events.h>
> +#include <xen/features.h>
> +#include <xen/interface/xen.h>
> +#include <xen/interface/vcpu.h>
> +#include <xen/xen-ops.h>
> +
> +/* runstate info updated by Xen */
> +static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
> +
> +/* return an consistent snapshot of 64-bit time/counter value */
> +static u64 get64(const u64 *p)
> +{
> +	u64 ret;
> +
> +	if (BITS_PER_LONG < 64) {
> +		u32 *p32 = (u32 *)p;
> +		u32 h, l;
> +
> +		/*
> +		 * Read high then low, and then make sure high is
> +		 * still the same; this will only loop if low wraps
> +		 * and carries into high.
> +		 * XXX some clean way to make this endian-proof?
> +		 */
> +		do {
> +			h = p32[1];
> +			barrier();
> +			l = p32[0];
> +			barrier();
> +		} while (p32[1] != h);
> +
> +		ret = (((u64)h) << 32) | l;
> +	} else
> +		ret = *p;
> +
> +	return ret;
> +}
> +
> +/*
> + * Runstate accounting
> + */
> +void xen_get_runstate_snapshot(struct vcpu_runstate_info *res)
> +{
> +	u64 state_time;
> +	struct vcpu_runstate_info *state;
> +
> +	BUG_ON(preemptible());
> +
> +	state = &__get_cpu_var(xen_runstate);
> +
> +	/*
> +	 * The runstate info is always updated by the hypervisor on
> +	 * the current CPU, so there's no need to use anything
> +	 * stronger than a compiler barrier when fetching it.
> +	 */
> +	do {
> +		state_time = get64(&state->state_entry_time);
> +		barrier();
> +		*res = *state;
> +		barrier();
> +	} while (get64(&state->state_entry_time) != state_time);
> +}
> +
> +/* return true when a vcpu could run but has no real cpu to run on */
> +bool xen_vcpu_stolen(int vcpu)
> +{
> +	return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
> +}
> +
> +void xen_setup_runstate_info(int cpu)
> +{
> +	struct vcpu_register_runstate_memory_area area;
> +
> +	area.addr.v = &per_cpu(xen_runstate, cpu);
> +
> +	if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area,
> +			       cpu, &area))
> +		BUG();

The original code did:

-       rc = HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area, cpu,
-                               &area);
-       WARN_ON(rc && rc != -ENOSYS);
-
Any reason not to do this?

> +}
> +
> diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
> index d6fe062..4fd4e47 100644
> --- a/include/xen/xen-ops.h
> +++ b/include/xen/xen-ops.h
> @@ -3,6 +3,7 @@
>  
>  #include <linux/percpu.h>
>  #include <asm/xen/interface.h>
> +#include <xen/interface/vcpu.h>
>  
>  DECLARE_PER_CPU(struct vcpu_info *, xen_vcpu);
>  
> @@ -16,6 +17,10 @@ void xen_mm_unpin_all(void);
>  void xen_timer_resume(void);
>  void xen_arch_resume(void);
>  
> +bool xen_vcpu_stolen(int vcpu);
> +void xen_setup_runstate_info(int cpu);
> +void xen_get_runstate_snapshot(struct vcpu_runstate_info *res);
> +
>  int xen_setup_shutdown_event(void);
>  
>  extern unsigned long *xen_contiguous_bitmap;
> -- 
> 1.7.2.5
>