[PATCH v10 0/5] xen/arm/arm64: CONFIG_PARAVIRT and stolen ticks accounting

[PATCH v10 0/5] xen/arm/arm64: CONFIG_PARAVIRT and stolen ticks accounting

[Stefano Stabellini]

Hi all,

I dusted off this series from Jan 2014. Patch #2 and #3 still need an ack.


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 v10:
- rebase
- remove ia64 xen changes
- add acks
- send the correct version of patch #2 (last time I sent an older
  version by mistake)
- remove ifdef CONFIG_PARAVIRT from kernel/sched/core.c
- replace "---help---" with "help" in arm and arm64 Kconfig changes


Stefano Stabellini (5):
      xen: move xen_setup_runstate_info and get_runstate_snapshot to drivers/xen/time.c
      missing include in cputime.c, remove #ifdef CONFIG_PARAVIRT from sched/core.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   |   20 ++++++++
 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 |   20 ++++++++
 arch/arm64/kernel/Makefile        |    1 +
 arch/arm64/kernel/paravirt.c      |   25 ++++++++++
 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 +
 15 files changed, 252 insertions(+), 78 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

Cheers,

Stefano

[PATCH v10 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 at oracle.com

---

Changes in v10:
- rebase
- remove ia64 changes
---
 arch/x86/xen/time.c   |   76 +----------------------------------------
 drivers/xen/Makefile  |    2 +-
 drivers/xen/time.c    |   91 +++++++++++++++++++++++++++++++++++++++++++++++++
 include/xen/xen-ops.h |    5 +++
 4 files changed, 98 insertions(+), 76 deletions(-)
 create mode 100644 drivers/xen/time.c

diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index f1ba6a0..041d4cd 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 = this_cpu_ptr(&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 e293bc5..943fb1c 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 balloon.o manage.o preempt.o
+obj-y	+= grant-table.o features.o balloon.o manage.o preempt.o time.o
 obj-y	+= events/
 obj-y	+= xenbus/
 
diff --git a/drivers/xen/time.c b/drivers/xen/time.c
new file mode 100644
index 0000000..433fe24
--- /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 = this_cpu_ptr(&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 e4e214a..86abe07 100644
--- a/include/xen/xen-ops.h
+++ b/include/xen/xen-ops.h
@@ -5,6 +5,7 @@
 #include <linux/notifier.h>
 #include <linux/efi.h>
 #include <asm/xen/interface.h>
+#include <xen/interface/vcpu.h>
 
 DECLARE_PER_CPU(struct vcpu_info *, xen_vcpu);
 
@@ -18,6 +19,10 @@ void xen_arch_suspend(void);
 void xen_resume_notifier_register(struct notifier_block *nb);
 void xen_resume_notifier_unregister(struct notifier_block *nb);
 
+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 v10 2/5] missing include in cputime.c, remove #ifdef CONFIG_PARAVIRT from sched/core.c

[Stefano Stabellini]

ifdef CONFIG_PARAVIRT in sched/core.c is redundant, as asm/paravirt.h
is already protected by #ifdef CONFIG_PARAVIRT.

Add include asm/paravirt.h to cputime.c, as steal_account_process_tick
calls paravirt_steal_clock, which is defined in paravirt.h.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
CC: mingo at redhat.com
CC: peterz at infradead.org
---
 kernel/sched/core.c    |    2 --
 kernel/sched/cputime.c |    1 +
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index bcd214e..395fad9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -79,9 +79,7 @@
 #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"
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 8cbc3db..a1426fa 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 v10 2/5] missing include in cputime.c, remove #ifdef CONFIG_PARAVIRT from sched/core.c

[kbuild test robot]

Hi Stefano,

[auto build test ERROR on arm64/for-next/core]
[cannot apply to: xen-tip/linux-next]
[also ERROR on: v4.3 next-20151103]

url:    https://github.com/0day-ci/linux/commits/Stefano-Stabellini/xen-arm-arm64-CONFIG_PARAVIRT-and-stolen-ticks-accounting/20151104-002433
base:   https://github.com/0day-ci/linux Stefano-Stabellini/xen-arm-arm64-CONFIG_PARAVIRT-and-stolen-ticks-accounting/20151104-002433
config: mips-jz4740 (attached as .config)
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=mips 

All errors (new ones prefixed by >>):

>> kernel/sched/core.c:82:26: fatal error: asm/paravirt.h: No such file or directory
   compilation terminated.
--
>> kernel/sched/cputime.c:8:26: fatal error: asm/paravirt.h: No such file or directory
   compilation terminated.

vim +82 kernel/sched/core.c

52f5684c kernel/sched/core.c Gideon Israel Dsouza  2014-04-07  76  #include <linux/compiler.h>
^1da177e kernel/sched.c      Linus Torvalds        2005-04-16  77  
96f951ed kernel/sched/core.c David Howells         2012-03-28  78  #include <asm/switch_to.h>
5517d86b kernel/sched.c      Eric Dumazet          2007-05-08  79  #include <asm/tlb.h>
838225b4 kernel/sched.c      Satyam Sharma         2007-10-24  80  #include <asm/irq_regs.h>
db7e527d kernel/sched/core.c Christian Borntraeger 2012-01-11  81  #include <asm/mutex.h>
e6e6685a kernel/sched.c      Glauber Costa         2011-07-11 @82  #include <asm/paravirt.h>
^1da177e kernel/sched.c      Linus Torvalds        2005-04-16  83  
029632fb kernel/sched.c      Peter Zijlstra        2011-10-25  84  #include "sched.h"
ea138446 kernel/sched/core.c Tejun Heo             2013-01-18  85  #include "../workqueue_internal.h"

:::::: The code at line 82 was first introduced by commit
:::::: e6e6685accfa81f509fadfc9624bc7c3862d75c4 KVM guest: Steal time accounting

:::::: TO: Glauber Costa <glommer@redhat.com>
:::::: CC: Avi Kivity <avi@redhat.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
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[PATCH v10 2/5] missing include in cputime.c, remove #ifdef CONFIG_PARAVIRT from sched/core.c

[Stefano Stabellini]

On Wed, 4 Nov 2015, kbuild test robot wrote:
> Hi Stefano,
> 
> [auto build test ERROR on arm64/for-next/core]
> [cannot apply to: xen-tip/linux-next]
> [also ERROR on: v4.3 next-20151103]
> 
> url:    https://github.com/0day-ci/linux/commits/Stefano-Stabellini/xen-arm-arm64-CONFIG_PARAVIRT-and-stolen-ticks-accounting/20151104-002433
> base:   https://github.com/0day-ci/linux Stefano-Stabellini/xen-arm-arm64-CONFIG_PARAVIRT-and-stolen-ticks-accounting/20151104-002433
> config: mips-jz4740 (attached as .config)

Ah, of course! I only tested x86, arm and arm64, but this wouldn't work
on any arches without arm/paravirt.h. Damn.

I guess we'll have to keep

#ifdef CONFIG_PARAVIRT
#include <asm/paravirt.h>
#endif


BTW this auto build test is awesome.

> reproduce:
>         wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         make.cross ARCH=mips 
> 
> All errors (new ones prefixed by >>):
> 
> >> kernel/sched/core.c:82:26: fatal error: asm/paravirt.h: No such file or directory
>    compilation terminated.
> --
> >> kernel/sched/cputime.c:8:26: fatal error: asm/paravirt.h: No such file or directory
>    compilation terminated.
> 
> vim +82 kernel/sched/core.c
> 
> 52f5684c kernel/sched/core.c Gideon Israel Dsouza  2014-04-07  76  #include <linux/compiler.h>
> ^1da177e kernel/sched.c      Linus Torvalds        2005-04-16  77  
> 96f951ed kernel/sched/core.c David Howells         2012-03-28  78  #include <asm/switch_to.h>
> 5517d86b kernel/sched.c      Eric Dumazet          2007-05-08  79  #include <asm/tlb.h>
> 838225b4 kernel/sched.c      Satyam Sharma         2007-10-24  80  #include <asm/irq_regs.h>
> db7e527d kernel/sched/core.c Christian Borntraeger 2012-01-11  81  #include <asm/mutex.h>
> e6e6685a kernel/sched.c      Glauber Costa         2011-07-11 @82  #include <asm/paravirt.h>
> ^1da177e kernel/sched.c      Linus Torvalds        2005-04-16  83  
> 029632fb kernel/sched.c      Peter Zijlstra        2011-10-25  84  #include "sched.h"
> ea138446 kernel/sched/core.c Tejun Heo             2013-01-18  85  #include "../workqueue_internal.h"
> 
> :::::: The code at line 82 was first introduced by commit
> :::::: e6e6685accfa81f509fadfc9624bc7c3862d75c4 KVM guest: Steal time accounting
> 
> :::::: TO: Glauber Costa <glommer@redhat.com>
> :::::: CC: Avi Kivity <avi@redhat.com>
> 
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
> 

[PATCH v10 2/5] missing include in cputime.c, remove #ifdef CONFIG_PARAVIRT from sched/core.c

[kbuild test robot]

Hi Stefano,

[auto build test ERROR on arm64/for-next/core]
[cannot apply to: xen-tip/linux-next]
[also ERROR on: v4.3 next-20151103]

url:    https://github.com/0day-ci/linux/commits/Stefano-Stabellini/xen-arm-arm64-CONFIG_PARAVIRT-and-stolen-ticks-accounting/20151104-002433
base:   https://github.com/0day-ci/linux Stefano-Stabellini/xen-arm-arm64-CONFIG_PARAVIRT-and-stolen-ticks-accounting/20151104-002433
config: avr32-atngw100_defconfig (attached as .config)
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=avr32 

All errors (new ones prefixed by >>):

>> kernel/sched/core.c:82:26: error: asm/paravirt.h: No such file or directory
--
>> kernel/sched/cputime.c:8:26: error: asm/paravirt.h: No such file or directory

vim +82 kernel/sched/core.c

52f5684c kernel/sched/core.c Gideon Israel Dsouza  2014-04-07  76  #include <linux/compiler.h>
^1da177e kernel/sched.c      Linus Torvalds        2005-04-16  77  
96f951ed kernel/sched/core.c David Howells         2012-03-28  78  #include <asm/switch_to.h>
5517d86b kernel/sched.c      Eric Dumazet          2007-05-08  79  #include <asm/tlb.h>
838225b4 kernel/sched.c      Satyam Sharma         2007-10-24  80  #include <asm/irq_regs.h>
db7e527d kernel/sched/core.c Christian Borntraeger 2012-01-11  81  #include <asm/mutex.h>
e6e6685a kernel/sched.c      Glauber Costa         2011-07-11 @82  #include <asm/paravirt.h>
^1da177e kernel/sched.c      Linus Torvalds        2005-04-16  83  
029632fb kernel/sched.c      Peter Zijlstra        2011-10-25  84  #include "sched.h"
ea138446 kernel/sched/core.c Tejun Heo             2013-01-18  85  #include "../workqueue_internal.h"

:::::: The code at line 82 was first introduced by commit
:::::: e6e6685accfa81f509fadfc9624bc7c3862d75c4 KVM guest: Steal time accounting

:::::: TO: Glauber Costa <glommer@redhat.com>
:::::: CC: Avi Kivity <avi@redhat.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
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[PATCH v10 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>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
CC: linux at arm.linux.org.uk
CC: will.deacon at arm.com
CC: nico at linaro.org
CC: marc.zyngier at arm.com
CC: cov at codeaurora.org
CC: arnd at arndb.de
CC: olof at lixom.net

---

Changes in v10:
- replace "---help---" with "help"

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/include/asm/paravirt.h |   20 ++++++++++++++++++++
 arch/arm/kernel/Makefile        |    1 +
 arch/arm/kernel/paravirt.c      |   25 +++++++++++++++++++++++++
 4 files changed, 66 insertions(+)
 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 639411f..8dfdaa6 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1819,6 +1819,25 @@ 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
@@ -1832,6 +1851,7 @@ config XEN
 	select ARCH_DMA_ADDR_T_64BIT
 	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/include/asm/paravirt.h b/arch/arm/include/asm/paravirt.h
new file mode 100644
index 0000000..8435ff59
--- /dev/null
+++ b/arch/arm/include/asm/paravirt.h
@@ -0,0 +1,20 @@
+#ifndef _ASM_ARM_PARAVIRT_H
+#define _ASM_ARM_PARAVIRT_H
+
+#ifdef CONFIG_PARAVIRT
+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
+
+#endif
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index af9e59b..3e6e937 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -81,6 +81,7 @@ obj-$(CONFIG_VDSO)		+= vdso.o
 ifneq ($(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);
-- 
1.7.10.4

[PATCH v10 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>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
CC: will.deacon at arm.com
CC: nico at linaro.org
CC: marc.zyngier at arm.com
CC: cov at codeaurora.org
CC: arnd at arndb.de
CC: olof at lixom.net
CC: Catalin.Marinas at arm.com

---

Changes in v10:
- replace "---help---" with "help"

Changes in v7:
- ifdef CONFIG_PARAVIRT the content of paravirt.h.
---
 arch/arm64/Kconfig                |   20 ++++++++++++++++++++
 arch/arm64/include/asm/paravirt.h |   20 ++++++++++++++++++++
 arch/arm64/kernel/Makefile        |    1 +
 arch/arm64/kernel/paravirt.c      |   25 +++++++++++++++++++++++++
 4 files changed, 66 insertions(+)
 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 07d1811..c8bd7dc 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -491,6 +491,25 @@ config SECCOMP
 	  and the task is only allowed to execute a few safe syscalls
 	  defined by each seccomp mode.
 
+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
@@ -499,6 +518,7 @@ config XEN
 	bool "Xen guest support on ARM64"
 	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/include/asm/paravirt.h b/arch/arm64/include/asm/paravirt.h
new file mode 100644
index 0000000..fd5f428
--- /dev/null
+++ b/arch/arm64/include/asm/paravirt.h
@@ -0,0 +1,20 @@
+#ifndef _ASM_ARM64_PARAVIRT_H
+#define _ASM_ARM64_PARAVIRT_H
+
+#ifdef CONFIG_PARAVIRT
+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
+
+#endif
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 22dc9bc..54fda9a 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -36,6 +36,7 @@ arm64-obj-$(CONFIG_EFI)			+= efi.o efi-stub.o efi-entry.o
 arm64-obj-$(CONFIG_PCI)			+= pci.o
 arm64-obj-$(CONFIG_ARMV8_DEPRECATED)	+= armv8_deprecated.o
 arm64-obj-$(CONFIG_ACPI)		+= acpi.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);
-- 
1.7.10.4

[PATCH v10 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 file changed, 21 insertions(+)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index eeeab07..7dd2cc0 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>
@@ -79,6 +82,19 @@ 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_percpu_init(void)
 {
 	struct vcpu_register_vcpu_info info;
@@ -96,6 +112,8 @@ static void xen_percpu_init(void)
 	BUG_ON(err);
 	per_cpu(xen_vcpu, cpu) = vcpup;
 
+	xen_setup_runstate_info(cpu);
+
 	enable_percpu_irq(xen_events_irq, 0);
 	put_cpu();
 }
@@ -259,6 +277,9 @@ 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);
+
 	return 0;
 }
 early_initcall(xen_guest_init);
-- 
1.7.10.4