[PATCH v8 0/6] xen/arm/arm64: CONFIG_PARAVIRT and stolen ticks accounting

[PATCH v8 0/6] 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


Changes in v8:
- rebased on 3.13-rc6.



Stefano Stabellini (6):
      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
      core: remove ifdef CONFIG_PARAVIRT
      xen/arm: account for stolen ticks

 arch/arm/Kconfig           |   20 ++++++++++
 arch/arm/kernel/Makefile   |    1 +
 arch/arm/xen/enlighten.c   |   21 ++++++++++
 arch/arm64/Kconfig         |   20 ++++++++++
 arch/arm64/kernel/Makefile |    1 +
 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/core.c        |    2 -
 kernel/sched/cputime.c     |    1 +
 12 files changed, 168 insertions(+), 120 deletions(-)
 create mode 100644 drivers/xen/time.c

git://git.kernel.org/pub/scm/linux/kernel/git/sstabellini/xen.git lost_ticks_8


Cheers,

Stefano

[PATCH v8 1/6] 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 12a1ca7..d479444 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -32,86 +32,12 @@
 #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);
 
 /* unused ns of stolen time */
 static DEFINE_PER_CPU(u64, xen_residual_stolen);
 
-/* 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;
@@ -119,7 +45,7 @@ static void do_stolen_accounting(void)
 	s64 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 14fe79d..cd95fb7 100644
--- a/drivers/xen/Makefile
+++ b/drivers/xen/Makefile
@@ -2,7 +2,7 @@ ifeq ($(filter y, $(CONFIG_ARM) $(CONFIG_ARM64)),)
 obj-$(CONFIG_HOTPLUG_CPU)		+= cpu_hotplug.o
 endif
 obj-$(CONFIG_X86)			+= fallback.o
-obj-y	+= grant-table.o features.o events.o balloon.o manage.o
+obj-y	+= grant-table.o features.o events.o balloon.o manage.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 fb2ea8f..ee3303b 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;
-- 
1.7.10.4

[PATCH v8 2/6] 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.

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

---

Changes in v7:
- remove ifdef CONFIG_PARAVIRT (the ifdef has been moved inside the
  paravirt headers).

Changes in v5:
- add ifdef CONFIG_PARAVIRT.
---
 kernel/sched/cputime.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 9994791..9f9b76a 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -5,6 +5,7 @@
 #include <linux/static_key.h>
 #include <linux/context_tracking.h>
 #include "sched.h"
+#include <asm/paravirt.h>
 
 
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
-- 
1.7.10.4

[PATCH v8 3/6] 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 v7:
- ifdef CONFIG_PARAVIRT the content of paravirt.h.

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/kernel/Makefile |    1 +
 2 files changed, 21 insertions(+)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c1f1a7e..d6c3ba1 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1874,6 +1874,25 @@ config SWIOTLB
 config IOMMU_HELPER
 	def_bool SWIOTLB
 
+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
@@ -1885,6 +1904,7 @@ config XEN
 	depends on !GENERIC_ATOMIC64
 	select ARM_PSCI
 	select SWIOTLB_XEN
+	select PARAVIRT
 	help
 	  Say Y if you want to run Linux in a Virtual Machine on Xen on ARM.
 
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index a30fc9b..bcd2b38 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -87,6 +87,7 @@ 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
-- 
1.7.10.4

[PATCH v8 4/6] 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

---

Changes in v7:
- ifdef CONFIG_PARAVIRT the content of paravirt.h.
---
 arch/arm64/Kconfig         |   20 ++++++++++++++++++++
 arch/arm64/kernel/Makefile |    1 +
 2 files changed, 21 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 6d4dd22..d1003ba 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -212,6 +212,25 @@ config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 
 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
@@ -220,6 +239,7 @@ config XEN
 	bool "Xen guest support on ARM64 (EXPERIMENTAL)"
 	depends on ARM64 && OF
 	select SWIOTLB_XEN
+	select PARAVIRT
 	help
 	  Say Y if you want to run Linux in a Virtual Machine on Xen on ARM64.
 
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 5ba2fd4..1dee735 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -18,6 +18,7 @@ arm64-obj-$(CONFIG_SMP)			+= smp.o smp_spin_table.o
 arm64-obj-$(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)
-- 
1.7.10.4

[PATCH v8 5/6] core: remove ifdef CONFIG_PARAVIRT

[Stefano Stabellini]

All the asm/paravirt.h headers (x86, ia64, arm, arm64) are properly
ifdef'ed CONFIG_PARAVIRT inside so they can be safely included.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
 kernel/sched/core.c |    2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a88f4a4..4f9b239 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -78,9 +78,7 @@
 #include <asm/tlb.h>
 #include <asm/irq_regs.h>
 #include <asm/mutex.h>
-#ifdef CONFIG_PARAVIRT
 #include <asm/paravirt.h>
-#endif
 
 #include "sched.h"
 #include "../workqueue_internal.h"
-- 
1.7.10.4

[PATCH v8 6/6] 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 file changed, 21 insertions(+)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 8550123..fa8bdc0 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>
@@ -154,6 +157,19 @@ 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;
@@ -171,6 +187,8 @@ 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);
 	put_cpu();
 }
@@ -313,6 +331,9 @@ 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);
-- 
1.7.10.4

Re: [PATCH v8 4/6] arm64: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops

[Christopher Covington]

Hi Stefano,

On 01/08/2014 01:49 PM, Stefano Stabellini wrote:
> 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

Looks good to me.

Acked-by Christopher Covington <cov@codeaurora.org>

While I don't think it should necessarily gate these changes, I wonder if at
some point the config options could be consolidated across the various
architectures using them.

Regards,
Christopher

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by the Linux Foundation.

Re: [PATCH v8 4/6] arm64: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops

[Catalin Marinas]

On Wed, Jan 08, 2014 at 06:49:56PM +0000, Stefano Stabellini wrote:
>  arch/arm64/Kconfig         |   20 ++++++++++++++++++++
>  arch/arm64/kernel/Makefile |    1 +
>  2 files changed, 21 insertions(+)
[...]
> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> index 5ba2fd4..1dee735 100644
> --- a/arch/arm64/kernel/Makefile
> +++ b/arch/arm64/kernel/Makefile
> @@ -18,6 +18,7 @@ arm64-obj-$(CONFIG_SMP)			+= smp.o smp_spin_table.o
>  arm64-obj-$(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

Did you forget a git add?

-- 
Catalin

Re: [PATCH v8 3/6] arm: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops

[Ian Campbell]

On Wed, 2014-01-08 at 18:49 +0000, Stefano Stabellini wrote:
> 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>

Acked-by: Ian Campbell <ian.campbell@citrix.com>

> 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 v7:
> - ifdef CONFIG_PARAVIRT the content of paravirt.h.
> 
> 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/kernel/Makefile |    1 +
>  2 files changed, 21 insertions(+)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index c1f1a7e..d6c3ba1 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1874,6 +1874,25 @@ config SWIOTLB
>  config IOMMU_HELPER
>  	def_bool SWIOTLB
>  
> +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
> @@ -1885,6 +1904,7 @@ config XEN
>  	depends on !GENERIC_ATOMIC64
>  	select ARM_PSCI
>  	select SWIOTLB_XEN
> +	select PARAVIRT
>  	help
>  	  Say Y if you want to run Linux in a Virtual Machine on Xen on ARM.
>  
> diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
> index a30fc9b..bcd2b38 100644
> --- a/arch/arm/kernel/Makefile
> +++ b/arch/arm/kernel/Makefile
> @@ -87,6 +87,7 @@ 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

Re: [PATCH v8 4/6] arm64: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops

[Ian Campbell]

On Thu, 2014-01-09 at 12:13 +0000, Catalin Marinas wrote:
> On Wed, Jan 08, 2014 at 06:49:56PM +0000, Stefano Stabellini wrote:
> >  arch/arm64/Kconfig         |   20 ++++++++++++++++++++
> >  arch/arm64/kernel/Makefile |    1 +
> >  2 files changed, 21 insertions(+)
> [...]
> > diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> > index 5ba2fd4..1dee735 100644
> > --- a/arch/arm64/kernel/Makefile
> > +++ b/arch/arm64/kernel/Makefile
> > @@ -18,6 +18,7 @@ arm64-obj-$(CONFIG_SMP)			+= smp.o smp_spin_table.o
> >  arm64-obj-$(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
> 
> Did you forget a git add?

I was just about to say the same thing for the previous arm patch too.

Ian.

Re: [PATCH v8 4/6] arm64: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops

[Stefano Stabellini]

On Thu, 9 Jan 2014, Ian Campbell wrote:
> On Thu, 2014-01-09 at 12:13 +0000, Catalin Marinas wrote:
> > On Wed, Jan 08, 2014 at 06:49:56PM +0000, Stefano Stabellini wrote:
> > >  arch/arm64/Kconfig         |   20 ++++++++++++++++++++
> > >  arch/arm64/kernel/Makefile |    1 +
> > >  2 files changed, 21 insertions(+)
> > [...]
> > > diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> > > index 5ba2fd4..1dee735 100644
> > > --- a/arch/arm64/kernel/Makefile
> > > +++ b/arch/arm64/kernel/Makefile
> > > @@ -18,6 +18,7 @@ arm64-obj-$(CONFIG_SMP)			+= smp.o smp_spin_table.o
> > >  arm64-obj-$(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
> > 
> > Did you forget a git add?
> 
> I was just about to say the same thing for the previous arm patch too.

That is what I get for still using patch queues :-/

Re: [PATCH v8 4/6] arm64: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops

[Catalin Marinas]

On Thu, Jan 09, 2014 at 05:50:44PM +0000, Stefano Stabellini wrote:
> On Thu, 9 Jan 2014, Ian Campbell wrote:
> > On Thu, 2014-01-09 at 12:13 +0000, Catalin Marinas wrote:
> > > On Wed, Jan 08, 2014 at 06:49:56PM +0000, Stefano Stabellini wrote:
> > > >  arch/arm64/Kconfig         |   20 ++++++++++++++++++++
> > > >  arch/arm64/kernel/Makefile |    1 +
> > > >  2 files changed, 21 insertions(+)
> > > [...]
> > > > diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> > > > index 5ba2fd4..1dee735 100644
> > > > --- a/arch/arm64/kernel/Makefile
> > > > +++ b/arch/arm64/kernel/Makefile
> > > > @@ -18,6 +18,7 @@ arm64-obj-$(CONFIG_SMP)			+= smp.o smp_spin_table.o
> > > >  arm64-obj-$(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
> > > 
> > > Did you forget a git add?
> > 
> > I was just about to say the same thing for the previous arm patch too.
> 
> That is what I get for still using patch queues :-/

You should upgrade to stgit ;)

-- 
Catalin