RE: VIRT-6865: Merge PARAVIRT_TIME_ACCOUNTING support

[Tim Montague]

Please ignore!

> -----Original Message-----
> From: Tim Montague [mailto:tmontague@xxxxxxx]
> Sent: Friday, August 23, 2019 11:27 AM
> To: Chad Page <chad.page@xxxxxxx>
> Cc: rtos-code-review@xxxxxxx; Stefano Stabellini
> <stefano.stabellini@xxxxxxxxxxxxx>; Mike Galbraith <efault@xxxxxx>; Peter
> Zijlstra <peterz@xxxxxxxxxxxxx>; Thomas Gleixner <tglx@xxxxxxxxxxxxx>;
> linux-kernel@xxxxxxxxxxxxxxx; Tim Montague <tmontague@xxxxxxx>
> Subject: VIRT-6865: Merge PARAVIRT_TIME_ACCOUNTING support
> 
> From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> 
> This is for the qualcomm-bsp-ghs_8x96autogvmquin44_d7 branch.
> 
> My checkout with this change is here:
> /home/cat/tmontague/linux-kernels/qualcomm-bsp-ghs
> Feel free to poke around.
> 
> 
> Commit message:
> 
> This is a combination of 2 commits:
> 
> commit 3f8f3fcd92d4c9fdcbf27eab39329c067521cf6a
>  Author: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
>  Date:   Mon Nov 23 10:33:49 2015 +0000
> ---
> arm64: introduce CONFIG_PARAVIRT, PARAVIRT_TIME_ACCOUNTING and
> pv_time_ops
> 
> 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>
> Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> 
> commit 692afb7fe6c312bcfb3e77913d1efa0cdedec5be
>  Author: Ingo Molnar <mingo@xxxxxxxxxx>
>  Date:   Thu Feb 2 14:47:27 2017 +0100
> ---
> sched/headers: Prepare header dependency changes, move the
> <asm/paravirt.h> include to kernel/sched/sched.h
> 
> Recent header reorganizations unearthed this hidden dependency:
> 
>   kernel/sched/core.c:199:25: error: 'paravirt_steal_rq_enabled' undeclared
> (first use in this function)
>   kernel/sched/core.c:200:11: error: implicit declaration of function
> 'paravirt_steal_clock' [-Werror=implicit-function-declaration]
> 
> So move the asm/paravirt.h include from kernel/sched/cpuclock.c to
> kernel/sched/sched.h.
> 
> ( NOTE: We do this change before doing the changes that introduce the build
> failure,
>         so the series remains fully bisectable. )
> 
> Reported-by: kbuild test robot <fengguang.wu@xxxxxxxxx>
> Acked-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Mike Galbraith <efault@xxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
> 
> Signed-off-by: Tim Montague <tmontague@xxxxxxx>
> ---
>  arch/arm64/Kconfig                | 20 ++++++++++++++++++++
>  arch/arm64/include/asm/paravirt.h | 20 ++++++++++++++++++++
>  arch/arm64/kernel/paravirt.c      | 25 +++++++++++++++++++++++++
>  kernel/sched/cputime.c            |  1 -
>  kernel/sched/sched.h              |  4 ++++
>  5 files changed, 69 insertions(+), 1 deletion(-)
>  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 0567e2121bc9..3984fbb10b9b 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -774,6 +774,25 @@ config SECCOMP
>  	  and the task is only allowed to execute a few safe syscalls
>  	  defined by each seccomp mode.
> 
> +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
> @@ -782,6 +801,7 @@ config XEN
>  	bool "Xen guest support on ARM64"
>  	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 000000000000..fd5f42886251
> --- /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/paravirt.c b/arch/arm64/kernel/paravirt.c
> new file mode 100644
> index 000000000000..53f371ed4568
> --- /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);
> diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
> index bd4ef2bb551e..01c2f225d0b0 100644
> --- a/kernel/sched/cputime.c
> +++ b/kernel/sched/cputime.c
> @@ -7,7 +7,6 @@
>  #include <linux/cpufreq_times.h>
>  #include "sched.h"
> 
> -
>  #ifdef CONFIG_IRQ_TIME_ACCOUNTING
> 
>  /*
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index b6cd12998f16..b2843f584029 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -10,6 +10,10 @@
>  #include <linux/tick.h>
>  #include <linux/slab.h>
> 
> +#ifdef CONFIG_PARAVIRT
> +#include <asm/paravirt.h>
> +#endif
> +
>  #include "cpupri.h"
>  #include "cpudeadline.h"
>  #include "cpuacct.h"
> --
> 2.17.1