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>
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.

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 49d993cee51232874a81814fe39ca99e09b88bad..5621a029729f2ff4dfd675882ddfc0a715dc91c4 100644 (file)
--- 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 (file)
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 5f3338eacad21024a75d7b1e7480f3fc58e804b8..d911db62d72a7066e7e50e7e2750290a757b4c6e 100644 (file)
--- 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 (file)
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);