[PATCH 0/6] Support calling functions on dedicated physical cpu

[PATCH 0/6] Support calling functions on dedicated physical cpu

[Juergen Gross]

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.

Juergen Gross (6):
  xen: sync xen header
  sched: add function to execute a function synchronously on a physical
    cpu
  dcdbas: make use of call_sync_on_phys_cpu()
  hwmon: use call_sync_on_phys_cpu() for dell-smm i8k
  virt, sched: add cpu pinning to call_sync_on_phys_cpu()
  xen: add xen_pin_vcpu() to support calling functions on a dedicated
    pcpu

 arch/x86/include/asm/hypervisor.h |   9 ++++
 arch/x86/xen/enlighten.c          |  40 +++++++++++++++
 drivers/firmware/dcdbas.c         |  46 ++++++++----------
 drivers/hwmon/dell-smm-hwmon.c    |  27 +++++-----
 include/linux/sched.h             |  31 ++++++++++++
 include/xen/interface/sched.h     | 100 +++++++++++++++++++++++++++++++-------
 kernel/sched/core.c               |  30 ++++++++++++
 7 files changed, 224 insertions(+), 59 deletions(-)

-- 
2.6.2


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Re: [PATCH 0/6] Support calling functions on dedicated physical cpu

[Peter Zijlstra]

On Fri, Mar 11, 2016 at 01:15:04PM +0000, One Thousand Gnomes wrote:
> On Fri, 11 Mar 2016 13:25:14 +0100
> Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > On Fri, Mar 11, 2016 at 12:59:28PM +0100, 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.  
> > 
> > So instead of telling Dell to get their act together and fix their damn
> > firmware, we're going to add the most horrid gunk to the kernel? How
> > does that make sense?
> 
> It's been normal forever. The convention with a lot of older BIOS crap
> was always that it should be called on the boot CPU (APM. PnPBIOS etc).
> 
> It's a stretch pre-EFI to even call it a "bug"

Yeah, I knew about the APM/PnP muck, but I was under the impression this
was about new hardware.


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Re: [PATCH 0/6] Support calling functions on dedicated physical cpu

[One Thousand Gnomes]

On Fri, 11 Mar 2016 13:25:14 +0100
Peter Zijlstra <peterz@infradead.org> wrote:

> On Fri, Mar 11, 2016 at 12:59:28PM +0100, 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.  
> 
> So instead of telling Dell to get their act together and fix their damn
> firmware, we're going to add the most horrid gunk to the kernel? How
> does that make sense?

It's been normal forever. The convention with a lot of older BIOS crap
was always that it should be called on the boot CPU (APM. PnPBIOS etc).

It's a stretch pre-EFI to even call it a "bug"

Alan

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Re: [PATCH 0/6] Support calling functions on dedicated physical cpu

[Pali Rohár]

On Friday 11 March 2016 13:25:14 Peter Zijlstra wrote:
> On Fri, Mar 11, 2016 at 12:59:28PM +0100, 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.
> 
> So instead of telling Dell to get their act together and fix their damn
> firmware, we're going to add the most horrid gunk to the kernel? How
> does that make sense?

Hi Peter! That problem is for old laptops and I doubt that Dell would
fix and distribute patches for 5-15 years old laptops...

-- 
Pali Rohár
pali.rohar@gmail.com

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Re: [PATCH 0/6] Support calling functions on dedicated physical cpu

[Peter Zijlstra]

On Fri, Mar 11, 2016 at 12:59:28PM +0100, 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.

So instead of telling Dell to get their act together and fix their damn
firmware, we're going to add the most horrid gunk to the kernel? How
does that make sense?

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