[Xen-devel] [PATCH v8 4/6] arm64: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
CC: will.deacon@xxxxxxx
CC: nico@xxxxxxxxxx
CC: marc.zyngier@xxxxxxx
CC: cov@xxxxxxxxxxxxxx
CC: arnd@xxxxxxxx
CC: olof@xxxxxxxxx
CC: Catalin.Marinas@xxxxxxx

---

Changes in v7:
- ifdef CONFIG_PARAVIRT the content of paravirt.h.
---
 arch/arm64/Kconfig         |   20 ++++++++++++++++++++
 arch/arm64/kernel/Makefile |    1 +
 2 files changed, 21 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 6d4dd22..d1003ba 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -212,6 +212,25 @@ config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 
 source "mm/Kconfig"
 
+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
@@ -220,6 +239,7 @@ config XEN
        bool "Xen guest support on ARM64 (EXPERIMENTAL)"
        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/kernel/Makefile b/arch/arm64/kernel/Makefile
index 5ba2fd4..1dee735 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -18,6 +18,7 @@ arm64-obj-$(CONFIG_SMP)                       += smp.o 
smp_spin_table.o
 arm64-obj-$(CONFIG_HW_PERF_EVENTS)     += perf_event.o
 arm64-obj-$(CONFIG_HAVE_HW_BREAKPOINT)+= hw_breakpoint.o
 arm64-obj-$(CONFIG_EARLY_PRINTK)       += early_printk.o
+arm64-obj-$(CONFIG_PARAVIRT)           += paravirt.o
 
 obj-y                                  += $(arm64-obj-y) vdso/
 obj-m                                  += $(arm64-obj-m)
-- 
1.7.10.4


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