[PATCH RFC v2 2/4] arm: introduce CONFIG_PARAVIRT and pv_time_ops

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

Introduce CONFIG_PARAVIRT on ARM.

The only paravirt interface supported is pv_time_ops.steal_clock.
No runtime pvops patching yet.

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


Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.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
---
 arch/arm/Kconfig                |    9 +++++++++
 arch/arm/include/asm/paravirt.h |   19 +++++++++++++++++++
 arch/arm/kernel/Makefile        |    1 +
 arch/arm/kernel/paravirt.c      |   32 ++++++++++++++++++++++++++++++++
 4 files changed, 61 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 344e299..35cb10a 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1887,12 +1887,21 @@ 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.  However, when run without a hypervisor
+	  the kernel is theoretically slower and slightly larger.
+
 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 dd9d90a..6764f60 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -86,5 +86,6 @@ ifeq ($(CONFIG_ARM_PSCI),y)
 obj-y				+= psci.o
 obj-$(CONFIG_SMP)		+= psci_smp.o
 endif
+obj-$(CONFIG_PARAVIRT)	+= paravirt.o
 
 extra-y := $(head-y) vmlinux.lds
diff --git a/arch/arm/kernel/paravirt.c b/arch/arm/kernel/paravirt.c
new file mode 100644
index 0000000..3e73fc8
--- /dev/null
+++ b/arch/arm/kernel/paravirt.c
@@ -0,0 +1,32 @@
+/*
+ * 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;
+
+static u64 native_steal_clock(int cpu)
+{
+	return 0;
+}
+
+struct pv_time_ops pv_time_ops = {
+	.steal_clock = native_steal_clock,
+};
+EXPORT_SYMBOL_GPL(pv_time_ops);
-- 
1.7.2.5