linux-kernel - Re: [PATCH v5 0/6] Support calling functions on dedicated physical cpu

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Message-ID: <570E07FD.4030403@suse.com>
Date:	Wed, 13 Apr 2016 10:49:01 +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 0/6] Support calling functions on dedicated physical
 cpu

On 06/04/16 16:17, Juergen Gross wrote:
> Some hardware (e.g. Dell Studio laptops) require special functions to
> be called on physical cpu 0 in order to avoid occasional hangs. When
> running as dom0 under Xen this could be achieved only via special boot
> parameters (vcpu pinning) limiting the hypervisor in it's scheduling
> decisions.
> 
> This patch series is adding a generic function to be able to temporarily
> pin a (virtual) cpu to a dedicated physical cpu for executing above
> mentioned functions on that specific cpu. The drivers (dcdbas and i8k)
> requiring this functionality are modified accordingly.
> 
> Changes in V5:
> - patch 3: rename and reshuffle parameters of smp_call_on_cpu() as requested
>   by Peter Zijlstra
> - patch 3: test target cpu to be online as requested by Peter Zijlstra
> - patch 4: less wordy messages as requested by David Vrabel
> 
> Changes in V4:
> - move patches 5 and 6 further up in the series
> - patch 2 (was 5): WARN_ONCE in case platform doesn't support pinning
>   as requested by Peter Zijlstra
> - patch 3 (was 2): change return value in case of illegal cpu as
>   requested by Peter Zijlstra
> - patch 3 (was 2): make pinning of vcpu an option as suggested by
>   Peter Zijlstra
> - patches 5 and 6 (were 3 and 4): add call to get_online_cpus()
> 
> Changes in V3:
> - use get_cpu()/put_cpu() as suggested by David Vrabel
> 
> Changes in V2:
> - instead of manipulating the allowed set of cpus use cpu specific
>   workqueue as requested by Peter Zijlstra
> - add include/linux/hypervisor.h to hide architecture specific stuff
>   from generic kernel code
> 
> Juergen Gross (6):
>   xen: sync xen header
>   virt, sched: add generic vcpu pinning support
>   smp: add function to execute a function synchronously on a cpu
>   xen: add xen_pin_vcpu() to support calling functions on a dedicated
>     pcpu
>   dcdbas: make use of smp_call_on_cpu()
>   hwmon: use smp_call_on_cpu() for dell-smm i8k
> 
>  MAINTAINERS                       |   1 +
>  arch/x86/include/asm/hypervisor.h |   4 ++
>  arch/x86/kernel/cpu/hypervisor.c  |  11 +++++
>  arch/x86/xen/enlighten.c          |  40 +++++++++++++++
>  drivers/firmware/dcdbas.c         |  51 +++++++++----------
>  drivers/hwmon/dell-smm-hwmon.c    |  35 +++++++------
>  include/linux/hypervisor.h        |  17 +++++++
>  include/linux/smp.h               |   3 ++
>  include/xen/interface/sched.h     | 100 +++++++++++++++++++++++++++++++-------
>  kernel/smp.c                      |  51 +++++++++++++++++++
>  kernel/up.c                       |  18 +++++++
>  11 files changed, 273 insertions(+), 58 deletions(-)
>  create mode 100644 include/linux/hypervisor.h
> 

So patches 1, 3 and 4 are acked. Any comments regarding patches 2, 5
and 6?


Juergen