[Xen-devel] [PATCH v8 3/6] arm: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
Acked-by: Christopher Covington <cov@xxxxxxxxxxxxxx>
CC: linux@xxxxxxxxxxxxxxxx
CC: will.deacon@xxxxxxx
CC: nico@xxxxxxxxxx
CC: marc.zyngier@xxxxxxx
CC: cov@xxxxxxxxxxxxxx
CC: arnd@xxxxxxxx
CC: olof@xxxxxxxxx

---

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


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