Re: [Xen-devel] [PATCH v9 4/5] arm64: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and pv_time_ops

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 9 Jan 2014, Stefano Stabellini wrote:
> 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

Catalin, Will, are you happy with this patch for 3.15?

 
> Changes in v7:
> - ifdef CONFIG_PARAVIRT the content of paravirt.h.
> ---
>  arch/arm64/Kconfig                |   20 ++++++++++++++++++++
>  arch/arm64/include/asm/paravirt.h |   20 ++++++++++++++++++++
>  arch/arm64/kernel/Makefile        |    1 +
>  arch/arm64/kernel/paravirt.c      |   25 +++++++++++++++++++++++++
>  4 files changed, 66 insertions(+)
>  create mode 100644 arch/arm64/include/asm/paravirt.h
>  create mode 100644 arch/arm64/kernel/paravirt.c
> 
> 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/include/asm/paravirt.h 
> b/arch/arm64/include/asm/paravirt.h
> new file mode 100644
> index 0000000..fd5f428
> --- /dev/null
> +++ b/arch/arm64/include/asm/paravirt.h
> @@ -0,0 +1,20 @@
> +#ifndef _ASM_ARM64_PARAVIRT_H
> +#define _ASM_ARM64_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/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)
> diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c
> new file mode 100644
> index 0000000..53f371e
> --- /dev/null
> +++ b/arch/arm64/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@xxxxxxxxxxxxx>
> + */
> +
> +#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);
> -- 
> 1.7.10.4
> 

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