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Message-ID: <alpine.DEB.2.02.1511101411570.5676@kaball.uk.xensource.com>
Date: Tue, 10 Nov 2015 14:12:57 +0000
From: Stefano Stabellini <stefano.stabellini@...citrix.com>
To: <linux-arm-kernel@...ts.infradead.org>
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>,
Christopher Covington <cov@...eaurora.org>,
Ian Campbell <ian.campbell@...rix.com>, <nico@...aro.org>,
<xen-devel@...ts.xensource.com>
Subject: Re: [PATCH v11 3/5] arm: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING
and pv_time_ops
On Thu, 5 Nov 2015, 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@...citrix.com>
> Acked-by: Christopher Covington <cov@...eaurora.org>
> Acked-by: Ian Campbell <ian.campbell@...rix.com>
> CC: linux@....linux.org.uk
> CC: will.deacon@....com
> CC: nico@...aro.org
> CC: marc.zyngier@....com
> CC: cov@...eaurora.org
> CC: arnd@...db.de
> CC: olof@...om.net
Russell,
are you OK with this patch?
>
> Changes in v10:
> - replace "---help---" with "help"
>
> 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/include/asm/paravirt.h | 20 ++++++++++++++++++++
> arch/arm/kernel/Makefile | 1 +
> arch/arm/kernel/paravirt.c | 25 +++++++++++++++++++++++++
> 4 files changed, 66 insertions(+)
> create mode 100644 arch/arm/include/asm/paravirt.h
> create mode 100644 arch/arm/kernel/paravirt.c
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index f1ed110..60be104 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1823,6 +1823,25 @@ 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
> @@ -1836,6 +1855,7 @@ config XEN
> select ARCH_DMA_ADDR_T_64BIT
> 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/include/asm/paravirt.h b/arch/arm/include/asm/paravirt.h
> new file mode 100644
> index 0000000..8435ff59
> --- /dev/null
> +++ b/arch/arm/include/asm/paravirt.h
> @@ -0,0 +1,20 @@
> +#ifndef _ASM_ARM_PARAVIRT_H
> +#define _ASM_ARM_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/arm/kernel/Makefile b/arch/arm/kernel/Makefile
> index af9e59b..3e6e937 100644
> --- a/arch/arm/kernel/Makefile
> +++ b/arch/arm/kernel/Makefile
> @@ -81,6 +81,7 @@ obj-$(CONFIG_VDSO) += vdso.o
> ifneq ($(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
> diff --git a/arch/arm/kernel/paravirt.c b/arch/arm/kernel/paravirt.c
> new file mode 100644
> index 0000000..53f371e
> --- /dev/null
> +++ b/arch/arm/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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