[PATCH v6 0/5] xen/arm/arm64: CONFIG_PARAVIRT and stolen ticks accounting

[PATCH v6 0/5] xen/arm/arm64: CONFIG_PARAVIRT and stolen ticks accounting

[Stefano Stabellini]

Hi all,
this patch series introduces stolen ticks accounting for Xen on ARM and
ARM64.
Stolen ticks are clocksource ticks that have been "stolen" from the cpu,
typically because Linux is running in a virtual machine and the vcpu has
been descheduled.
To account for these ticks we introduce CONFIG_PARAVIRT and pv_time_ops
so that we can make use of:

kernel/sched/cputime.c:steal_account_process_tick


In this last iteration I have added support for stolen ticks to arm64
and rebased on Catalin's upstream branch (that contains support for Xen
on arm64).



Stefano Stabellini (5):
      xen: move xen_setup_runstate_info and get_runstate_snapshot to drivers/xen/time.c
      kernel: missing include in cputime.c
      arm: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops
      arm64: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops
      xen/arm: account for stolen ticks

 arch/arm/Kconfig                  |   20 ++++++++
 arch/arm/include/asm/paravirt.h   |   19 ++++++++
 arch/arm/kernel/Makefile          |    1 +
 arch/arm/kernel/paravirt.c        |   25 ++++++++++
 arch/arm/xen/enlighten.c          |   21 +++++++++
 arch/arm64/Kconfig                |   20 ++++++++
 arch/arm64/include/asm/paravirt.h |   19 ++++++++
 arch/arm64/kernel/Makefile        |    1 +
 arch/arm64/kernel/paravirt.c      |   25 ++++++++++
 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 ++
 kernel/sched/cputime.c            |    4 +-
 15 files changed, 258 insertions(+), 119 deletions(-)
 create mode 100644 arch/arm/include/asm/paravirt.h
 create mode 100644 arch/arm/kernel/paravirt.c
 create mode 100644 arch/arm64/include/asm/paravirt.h
 create mode 100644 arch/arm64/kernel/paravirt.c
 create mode 100644 drivers/xen/time.c


git://git.kernel.org/pub/scm/linux/kernel/git/sstabellini/xen.git lost_ticks_6

Cheers,

Stefano

[PATCH v6 1/5] xen: move xen_setup_runstate_info and get_runstate_snapshot to drivers/xen/time.c

[Stefano Stabellini]

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.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.
---
 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();
+}
+
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

[PATCH v6 2/5] kernel: missing include in cputime.c

[Stefano Stabellini]

steal_account_process_tick calls paravirt_steal_clock, but paravirt.h is
currently missing amoung the included header files.
Add include asm/paravirt.h ifdef CONFIG_PARAVIRT.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
CC: mingo@redhat.com
CC: peterz@infradead.org

Changes in v5:
- add ifdef CONFIG_PARAVIRT.
---
 kernel/sched/cputime.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index cc2dc3ee..317a578 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -5,7 +5,9 @@
 #include <linux/static_key.h>
 #include <linux/context_tracking.h>
 #include "sched.h"
-
+#ifdef CONFIG_PARAVIRT
+#include <asm/paravirt.h>
+#endif
 
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
 
-- 
1.7.2.5

Re: [PATCH v6 2/5] kernel: missing include in cputime.c

[Peter Zijlstra]

On Thu, Jun 27, 2013 at 02:54:29PM +0100, Stefano Stabellini wrote:
> steal_account_process_tick calls paravirt_steal_clock, but paravirt.h is
> currently missing amoung the included header files.
> Add include asm/paravirt.h ifdef CONFIG_PARAVIRT.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> CC: mingo@redhat.com
> CC: peterz@infradead.org
> 
> Changes in v5:
> - add ifdef CONFIG_PARAVIRT.
> ---
>  kernel/sched/cputime.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
> index cc2dc3ee..317a578 100644
> --- a/kernel/sched/cputime.c
> +++ b/kernel/sched/cputime.c
> @@ -5,7 +5,9 @@
>  #include <linux/static_key.h>
>  #include <linux/context_tracking.h>
>  #include "sched.h"
> -
> +#ifdef CONFIG_PARAVIRT
> +#include <asm/paravirt.h>
> +#endif

Why isn't that CONFIG stuff inside the header instead of around it?

Re: [PATCH v6 2/5] kernel: missing include in cputime.c

[Ingo Molnar]

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Thu, Jun 27, 2013 at 02:54:29PM +0100, Stefano Stabellini wrote:
> > steal_account_process_tick calls paravirt_steal_clock, but paravirt.h is
> > currently missing amoung the included header files.
> > Add include asm/paravirt.h ifdef CONFIG_PARAVIRT.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> > CC: mingo@redhat.com
> > CC: peterz@infradead.org
> > 
> > Changes in v5:
> > - add ifdef CONFIG_PARAVIRT.
> > ---
> >  kernel/sched/cputime.c |    4 +++-
> >  1 files changed, 3 insertions(+), 1 deletions(-)
> > 
> > diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
> > index cc2dc3ee..317a578 100644
> > --- a/kernel/sched/cputime.c
> > +++ b/kernel/sched/cputime.c
> > @@ -5,7 +5,9 @@
> >  #include <linux/static_key.h>
> >  #include <linux/context_tracking.h>
> >  #include "sched.h"
> > -
> > +#ifdef CONFIG_PARAVIRT
> > +#include <asm/paravirt.h>
> > +#endif
> 
> Why isn't that CONFIG stuff inside the header instead of around it?

Indeed.

Once that is fixed then the #ifdef around asm/paravirt.h in 
kernel/sched/core.c could be removed as well.

Thanks,

	Ingo

Re: [PATCH v6 2/5] kernel: missing include in cputime.c

[Stefano Stabellini]

On Thu, 27 Jun 2013, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > On Thu, Jun 27, 2013 at 02:54:29PM +0100, Stefano Stabellini wrote:
> > > steal_account_process_tick calls paravirt_steal_clock, but paravirt.h is
> > > currently missing amoung the included header files.
> > > Add include asm/paravirt.h ifdef CONFIG_PARAVIRT.
> > > 
> > > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> > > CC: mingo@redhat.com
> > > CC: peterz@infradead.org
> > > 
> > > Changes in v5:
> > > - add ifdef CONFIG_PARAVIRT.
> > > ---
> > >  kernel/sched/cputime.c |    4 +++-
> > >  1 files changed, 3 insertions(+), 1 deletions(-)
> > > 
> > > diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
> > > index cc2dc3ee..317a578 100644
> > > --- a/kernel/sched/cputime.c
> > > +++ b/kernel/sched/cputime.c
> > > @@ -5,7 +5,9 @@
> > >  #include <linux/static_key.h>
> > >  #include <linux/context_tracking.h>
> > >  #include "sched.h"
> > > -
> > > +#ifdef CONFIG_PARAVIRT
> > > +#include <asm/paravirt.h>
> > > +#endif
> > 
> > Why isn't that CONFIG stuff inside the header instead of around it?
> 
> Indeed.
> 
> Once that is fixed then the #ifdef around asm/paravirt.h in 
> kernel/sched/core.c could be removed as well.

Right, that should work.
I'll make the change and resend with an additional patch to remove the
ifdef in kernel/sched/core.c.

[PATCH v6 3/5] arm: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops

[Stefano Stabellini]

Introduce CONFIG_PARAVIRT and PARAVIRT_TIME_ACCOUNTING on ARM.

The only paravirt interface supported is pv_time_ops.steal_clock, so no
runtime pvops patching needed.

This allows us to make use of steal_account_process_tick for stolen
ticks accounting.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Christopher Covington <cov@codeaurora.org>
CC: linux@arm.linux.org.uk
CC: will.deacon@arm.com
CC: nico@linaro.org
CC: marc.zyngier@arm.com
CC: cov@codeaurora.org
CC: arnd@arndb.de
CC: olof@lixom.net

Changes in v3:
- improve commit description and Kconfig help text;
- no need to initialize pv_time_ops;
- add PARAVIRT_TIME_ACCOUNTING.
---
 arch/arm/Kconfig                |   20 ++++++++++++++++++++
 arch/arm/include/asm/paravirt.h |   19 +++++++++++++++++++
 arch/arm/kernel/Makefile        |    1 +
 arch/arm/kernel/paravirt.c      |   25 +++++++++++++++++++++++++
 4 files changed, 65 insertions(+), 0 deletions(-)
 create mode 100644 arch/arm/include/asm/paravirt.h
 create mode 100644 arch/arm/kernel/paravirt.c

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 49d993c..5621a02 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1786,12 +1786,32 @@ config XEN_DOM0
 	def_bool y
 	depends on XEN
 
+config PARAVIRT
+	bool "Enable paravirtualization code"
+	---help---
+	  This changes the kernel so it can modify itself when it is run
+	  under a hypervisor, potentially improving performance significantly
+	  over full virtualization.
+
+config PARAVIRT_TIME_ACCOUNTING
+	bool "Paravirtual steal time accounting"
+	select PARAVIRT
+	default n
+	---help---
+	  Select this option to enable fine granularity task steal time
+	  accounting. Time spent executing other tasks in parallel with
+	  the current vCPU is discounted from the vCPU power. To account for
+	  that, there can be a small performance impact.
+
+	  If in doubt, say N here.
+
 config XEN
 	bool "Xen guest support on ARM (EXPERIMENTAL)"
 	depends on ARM && AEABI && OF
 	depends on CPU_V7 && !CPU_V6
 	depends on !GENERIC_ATOMIC64
 	select ARM_PSCI
+	select PARAVIRT
 	help
 	  Say Y if you want to run Linux in a Virtual Machine on Xen on ARM.
 
diff --git a/arch/arm/include/asm/paravirt.h b/arch/arm/include/asm/paravirt.h
new file mode 100644
index 0000000..3b95bc6
--- /dev/null
+++ b/arch/arm/include/asm/paravirt.h
@@ -0,0 +1,19 @@
+#ifndef _ASM_ARM_PARAVIRT_H
+#define _ASM_ARM_PARAVIRT_H
+
+struct static_key;
+extern struct static_key paravirt_steal_enabled;
+extern struct static_key paravirt_steal_rq_enabled;
+
+struct pv_time_ops {
+	unsigned long long (*steal_clock)(int cpu);
+};
+extern struct pv_time_ops pv_time_ops;
+
+static inline u64 paravirt_steal_clock(int cpu)
+{
+	return pv_time_ops.steal_clock(cpu);
+}
+
+
+#endif
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 5f3338e..d911db6 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -76,6 +76,7 @@ obj-$(CONFIG_ARM_CPU_TOPOLOGY)  += topology.o
 ifneq ($(CONFIG_ARCH_EBSA110),y)
   obj-y		+= io.o
 endif
+obj-$(CONFIG_PARAVIRT)	+= paravirt.o
 
 head-y			:= head$(MMUEXT).o
 obj-$(CONFIG_DEBUG_LL)	+= debug.o
diff --git a/arch/arm/kernel/paravirt.c b/arch/arm/kernel/paravirt.c
new file mode 100644
index 0000000..53f371e
--- /dev/null
+++ b/arch/arm/kernel/paravirt.c
@@ -0,0 +1,25 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * Copyright (C) 2013 Citrix Systems
+ *
+ * Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
+ */
+
+#include <linux/export.h>
+#include <linux/jump_label.h>
+#include <linux/types.h>
+#include <asm/paravirt.h>
+
+struct static_key paravirt_steal_enabled;
+struct static_key paravirt_steal_rq_enabled;
+
+struct pv_time_ops pv_time_ops;
+EXPORT_SYMBOL_GPL(pv_time_ops);
-- 
1.7.2.5

[PATCH v6 4/5] arm64: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops

[Stefano Stabellini]

Introduce CONFIG_PARAVIRT and PARAVIRT_TIME_ACCOUNTING on ARM64.
Necessary duplication of paravirt.h and paravirt.c with ARM.

The only paravirt interface supported is pv_time_ops.steal_clock, so no
runtime pvops patching needed.

This allows us to make use of steal_account_process_tick for stolen
ticks accounting.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
CC: will.deacon@arm.com
CC: nico@linaro.org
CC: marc.zyngier@arm.com
CC: cov@codeaurora.org
CC: arnd@arndb.de
CC: olof@lixom.net
CC: Catalin.Marinas@arm.com
---
 arch/arm64/Kconfig                |   20 ++++++++++++++++++++
 arch/arm64/include/asm/paravirt.h |   19 +++++++++++++++++++
 arch/arm64/kernel/Makefile        |    1 +
 arch/arm64/kernel/paravirt.c      |   25 +++++++++++++++++++++++++
 4 files changed, 65 insertions(+), 0 deletions(-)
 create mode 100644 arch/arm64/include/asm/paravirt.h
 create mode 100644 arch/arm64/kernel/paravirt.c

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1fac4e5..4c4f213 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -190,6 +190,25 @@ config HW_PERF_EVENTS
 
 source "mm/Kconfig"
 
+config PARAVIRT
+	bool "Enable paravirtualization code"
+	---help---
+	  This changes the kernel so it can modify itself when it is run
+	  under a hypervisor, potentially improving performance significantly
+	  over full virtualization.
+
+config PARAVIRT_TIME_ACCOUNTING
+	bool "Paravirtual steal time accounting"
+	select PARAVIRT
+	default n
+	---help---
+	  Select this option to enable fine granularity task steal time
+	  accounting. Time spent executing other tasks in parallel with
+	  the current vCPU is discounted from the vCPU power. To account for
+	  that, there can be a small performance impact.
+
+	  If in doubt, say N here.
+
 config XEN_DOM0
 	def_bool y
 	depends on XEN
@@ -197,6 +216,7 @@ config XEN_DOM0
 config XEN
 	bool "Xen guest support on ARM64 (EXPERIMENTAL)"
 	depends on ARM64 && OF
+	select PARAVIRT
 	help
 	  Say Y if you want to run Linux in a Virtual Machine on Xen on ARM64.
 
diff --git a/arch/arm64/include/asm/paravirt.h b/arch/arm64/include/asm/paravirt.h
new file mode 100644
index 0000000..54e895b
--- /dev/null
+++ b/arch/arm64/include/asm/paravirt.h
@@ -0,0 +1,19 @@
+#ifndef _ASM_ARM64_PARAVIRT_H
+#define _ASM_ARM64_PARAVIRT_H
+
+struct static_key;
+extern struct static_key paravirt_steal_enabled;
+extern struct static_key paravirt_steal_rq_enabled;
+
+struct pv_time_ops {
+	unsigned long long (*steal_clock)(int cpu);
+};
+extern struct pv_time_ops pv_time_ops;
+
+static inline u64 paravirt_steal_clock(int cpu)
+{
+	return pv_time_ops.steal_clock(cpu);
+}
+
+
+#endif
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 7b4b564..17613ad 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -18,6 +18,7 @@ arm64-obj-$(CONFIG_SMP)			+= smp.o smp_spin_table.o smp_psci.o
 arm64-obj-$(CONFIG_HW_PERF_EVENTS)	+= perf_event.o
 arm64-obj-$(CONFIG_HAVE_HW_BREAKPOINT)+= hw_breakpoint.o
 arm64-obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o
+arm64-obj-$(CONFIG_PARAVIRT)		+= paravirt.o
 
 obj-y					+= $(arm64-obj-y) vdso/
 obj-m					+= $(arm64-obj-m)
diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c
new file mode 100644
index 0000000..53f371e
--- /dev/null
+++ b/arch/arm64/kernel/paravirt.c
@@ -0,0 +1,25 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * Copyright (C) 2013 Citrix Systems
+ *
+ * Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
+ */
+
+#include <linux/export.h>
+#include <linux/jump_label.h>
+#include <linux/types.h>
+#include <asm/paravirt.h>
+
+struct static_key paravirt_steal_enabled;
+struct static_key paravirt_steal_rq_enabled;
+
+struct pv_time_ops pv_time_ops;
+EXPORT_SYMBOL_GPL(pv_time_ops);
-- 
1.7.2.5

[PATCH v6 5/5] xen/arm: account for stolen ticks

[Stefano Stabellini]

Register the runstate_memory_area with the hypervisor.
Use pv_time_ops.steal_clock to account for stolen ticks.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>


Changes in v4:
- don't use paravirt_steal_rq_enabled: we do not support retrieving
stolen ticks for vcpus other than one we are running on.

Changes in v3:
- use BUG_ON and smp_processor_id.
---
 arch/arm/xen/enlighten.c |   21 +++++++++++++++++++++
 1 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 13609e0..49839d8 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -14,7 +14,10 @@
 #include <xen/xen-ops.h>
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
+#include <asm/arch_timer.h>
 #include <asm/system_misc.h>
+#include <asm/paravirt.h>
+#include <linux/jump_label.h>
 #include <linux/interrupt.h>
 #include <linux/irqreturn.h>
 #include <linux/module.h>
@@ -152,6 +155,19 @@ int xen_unmap_domain_mfn_range(struct vm_area_struct *vma,
 }
 EXPORT_SYMBOL_GPL(xen_unmap_domain_mfn_range);
 
+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 __init xen_percpu_init(void *unused)
 {
 	struct vcpu_register_vcpu_info info;
@@ -169,6 +185,8 @@ static void __init xen_percpu_init(void *unused)
 	BUG_ON(err);
 	per_cpu(xen_vcpu, cpu) = vcpup;
 
+	xen_setup_runstate_info(cpu);
+
 	enable_percpu_irq(xen_events_irq, 0);
 }
 
@@ -300,6 +318,9 @@ static int __init xen_init_events(void)
 
 	on_each_cpu(xen_percpu_init, NULL, 0);
 
+	pv_time_ops.steal_clock = xen_stolen_accounting;
+	static_key_slow_inc(&paravirt_steal_enabled);
+
 	return 0;
 }
 postcore_initcall(xen_init_events);
-- 
1.7.2.5