arm: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops

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>
Acked-by: Russell King <linux@arm.linux.org.uk>

4 files changed, 66 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 34e1569a11ee..1ab9b98d4c6c 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1800,6 +1800,25 @@ 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
@@ -1813,6 +1832,7 @@ 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 000000000000..8435ff591386
--- /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 af9e59bf3831..3e6e93725ca7 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 000000000000..53f371ed4568
--- /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);