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

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, May 29, 2013 at 12:03:26PM +0100, Stefano Stabellini wrote:
> On Tue, 28 May 2013, Konrad Rzeszutek Wilk wrote:
> > On Tue, May 28, 2013 at 06:54:29PM +0100, Stefano Stabellini wrote:
> > > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > > Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > > CC: konrad.wilk@xxxxxxxxxx
> > > 
> > > 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.
> 
> do_stolen_accounting? Just enought to call the new common function
> xen_get_runstate_snapshot instead of the old x86 specific
> get_runstate_snapshot.
> 
> 
> > > ---
> > >  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?
> 
> The original x86 code just BUGs out: I took that version over the ia64
> version.

Ah, I see it now. OK, then this looks good to me.

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