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

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Message-ID: <57710150.8020800@suse.com>
Date:	Mon, 27 Jun 2016 12:34:56 +0200
From:	Juergen Gross <jgross@...e.com>
To:	linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
	david.vrabel@...rix.com
Cc:	boris.ostrovsky@...cle.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.

David, as I've got no reactions when asking for the last outstanding
Acks (patches 2 and 5) and neither Ingo nor Peter seem to be willing
to take the patches, I'd like to suggest we carry the series via the
xen tree. Are you okay with this suggestion?


Juergen

> 
> 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
>