linux-kernel - Re: [PATCH v5 2/6] virt, sched: add generic vcpu pinning support

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Date:	Wed, 15 Jun 2016 13:18:47 +0200
From:	Juergen Gross <jgross@...e.com>
To:	linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org
Cc:	boris.ostrovsky@...cle.com, david.vrabel@...rix.com,
	mingo@...hat.com, peterz@...radead.org, Douglas_Warzecha@...l.com,
	pali.rohar@...il.com, jdelvare@...e.com, linux@...ck-us.net,
	tglx@...utronix.de, hpa@...or.com, jeremy@...p.org,
	chrisw@...s-sol.org, akataria@...are.com, rusty@...tcorp.com.au,
	virtualization@...ts.linux-foundation.org, x86@...nel.org
Subject: Re: [PATCH v5 2/6] virt, sched: add generic vcpu pinning support

On 06/04/16 16:17, Juergen Gross wrote:
> Add generic virtualization support for pinning the current vcpu to a
> specified physical cpu. As this operation isn't performance critical
> (a very limited set of operations like BIOS calls and SMIs is expected
> to need this) just add a hypervisor specific indirection.
>
> Signed-off-by: Juergen Gross <jgross@...e.com>

Could please some maintainer comment on this patch?


Juergen

> ---
> V4: move this patch some places up in the series
>      WARN_ONCE in case platform doesn't support pinning as requested by
>      Peter Zijlstra
>
> V3: use getc_cpu()/put_cpu() as suggested by David Vrabel
>
> V2: adapt to using workqueues
>      add include/linux/hypervisor.h to hide architecture specific stuff
>      from generic kernel code
>
> In case paravirt maintainers don't want to be responsible for
> include/linux/hypervisor.h I could take it.
> ---
>   MAINTAINERS                       |  1 +
>   arch/x86/include/asm/hypervisor.h |  4 ++++
>   arch/x86/kernel/cpu/hypervisor.c  | 11 +++++++++++
>   include/linux/hypervisor.h        | 17 +++++++++++++++++
>   kernel/smp.c                      |  1 +
>   kernel/up.c                       |  1 +
>   6 files changed, 35 insertions(+)
>   create mode 100644 include/linux/hypervisor.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 40eb1db..d3bde4f 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -8330,6 +8330,7 @@ S:	Supported
>   F:	Documentation/virtual/paravirt_ops.txt
>   F:	arch/*/kernel/paravirt*
>   F:	arch/*/include/asm/paravirt.h
> +F:	include/linux/hypervisor.h
>
>   PARIDE DRIVERS FOR PARALLEL PORT IDE DEVICES
>   M:	Tim Waugh <tim@...erelk.net>
> diff --git a/arch/x86/include/asm/hypervisor.h b/arch/x86/include/asm/hypervisor.h
> index 055ea99..67942b6 100644
> --- a/arch/x86/include/asm/hypervisor.h
> +++ b/arch/x86/include/asm/hypervisor.h
> @@ -43,6 +43,9 @@ struct hypervisor_x86 {
>
>   	/* X2APIC detection (run once per boot) */
>   	bool		(*x2apic_available)(void);
> +
> +	/* pin current vcpu to specified physical cpu (run rarely) */
> +	void		(*pin_vcpu)(int);
>   };
>
>   extern const struct hypervisor_x86 *x86_hyper;
> @@ -56,6 +59,7 @@ extern const struct hypervisor_x86 x86_hyper_kvm;
>   extern void init_hypervisor(struct cpuinfo_x86 *c);
>   extern void init_hypervisor_platform(void);
>   extern bool hypervisor_x2apic_available(void);
> +extern void hypervisor_pin_vcpu(int cpu);
>   #else
>   static inline void init_hypervisor(struct cpuinfo_x86 *c) { }
>   static inline void init_hypervisor_platform(void) { }
> diff --git a/arch/x86/kernel/cpu/hypervisor.c b/arch/x86/kernel/cpu/hypervisor.c
> index 73d391a..ff108f8 100644
> --- a/arch/x86/kernel/cpu/hypervisor.c
> +++ b/arch/x86/kernel/cpu/hypervisor.c
> @@ -85,3 +85,14 @@ bool __init hypervisor_x2apic_available(void)
>   	       x86_hyper->x2apic_available &&
>   	       x86_hyper->x2apic_available();
>   }
> +
> +void hypervisor_pin_vcpu(int cpu)
> +{
> +	if (!x86_hyper)
> +		return;
> +
> +	if (x86_hyper->pin_vcpu)
> +		x86_hyper->pin_vcpu(cpu);
> +	else
> +		WARN_ONCE(1, "vcpu pinning requested but not supported!\n");
> +}
> diff --git a/include/linux/hypervisor.h b/include/linux/hypervisor.h
> new file mode 100644
> index 0000000..3fa5ef2
> --- /dev/null
> +++ b/include/linux/hypervisor.h
> @@ -0,0 +1,17 @@
> +#ifndef __LINUX_HYPEVISOR_H
> +#define __LINUX_HYPEVISOR_H
> +
> +/*
> + *	Generic Hypervisor support
> + *		Juergen Gross <jgross@...e.com>
> + */
> +
> +#ifdef CONFIG_HYPERVISOR_GUEST
> +#include <asm/hypervisor.h>
> +#else
> +static inline void hypervisor_pin_vcpu(int cpu)
> +{
> +}
> +#endif
> +
> +#endif /* __LINUX_HYPEVISOR_H */
> diff --git a/kernel/smp.c b/kernel/smp.c
> index 7416544..9388064 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -14,6 +14,7 @@
>   #include <linux/smp.h>
>   #include <linux/cpu.h>
>   #include <linux/sched.h>
> +#include <linux/hypervisor.h>
>
>   #include "smpboot.h"
>
> diff --git a/kernel/up.c b/kernel/up.c
> index 1760bf3..3ccee2b 100644
> --- a/kernel/up.c
> +++ b/kernel/up.c
> @@ -6,6 +6,7 @@
>   #include <linux/kernel.h>
>   #include <linux/export.h>
>   #include <linux/smp.h>
> +#include <linux/hypervisor.h>
>
>   int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
>   				int wait)
>