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Date: Mon, 17 Feb 2014 12:25:42 +0000
From: Stefano Stabellini <stefano.stabellini@...citrix.com>
To: <Catalin.Marinas@....com>
CC: <xen-devel@...ts.xensource.com>, <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>, <konrad.wilk@...cle.com>,
<marc.zyngier@....com>, <will.deacon@....com>,
Ian Campbell <Ian.Campbell@...rix.com>,
<linux@....linux.org.uk>, <olof@...om.net>, <arnd@...db.de>,
<catalin.marinas@....com>, <nico@...aro.org>, <cov@...eaurora.org>,
<xen-devel@...ts.xensource.com>
Subject: Re: [PATCH v9 4/5] arm64: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING
and pv_time_ops
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@...citrix.com>
> CC: will.deacon@....com
> CC: nico@...aro.org
> CC: marc.zyngier@....com
> CC: cov@...eaurora.org
> CC: arnd@...db.de
> CC: olof@...om.net
> CC: Catalin.Marinas@....com
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@...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);
> --
> 1.7.10.4
>
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