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



On Wed, 2014-01-08 at 18:49 +0000, Stefano Stabellini wrote:
> 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>

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

> 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



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