linux-kernel - Re: [PATCH v3 0/4] implement vcpu preempted check

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Message-Id: <166f3bad-f700-4624-6c1c-996f90ad609c@de.ibm.com>
Date:   Thu, 29 Sep 2016 12:23:19 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        virtualization@...ts.linux-foundation.org,
        linux-s390@...r.kernel.org, xen-devel-request@...ts.xenproject.org,
        kvm@...r.kernel.org, benh@...nel.crashing.org, paulus@...ba.org,
        mpe@...erman.id.au, mingo@...hat.com, paulmck@...ux.vnet.ibm.com,
        will.deacon@....com, kernellwp@...il.com, jgross@...e.com,
        pbonzini@...hat.com, bsingharora@...il.com,
        linux-s390 <linux-s390@...r.kernel.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH v3 0/4] implement vcpu preempted check

On 09/29/2016 12:10 PM, Peter Zijlstra wrote:
> On Thu, Jul 21, 2016 at 07:45:10AM -0400, Pan Xinhui wrote:
>> change from v2:
>> 	no code change, fix typos, update some comments
>>
>> change from v1:
>> 	a simplier definition of default vcpu_is_preempted
>> 	skip mahcine type check on ppc, and add config. remove dedicated macro.
>> 	add one patch to drop overload of rwsem_spin_on_owner and mutex_spin_on_owner. 
>> 	add more comments
>> 	thanks boqun and Peter's suggestion.
>>
>> This patch set aims to fix lock holder preemption issues.
> 
> So I really like the concept, but I would also really like to see
> support for more hypervisors included before we can move forward with
> this.
> 
> Please consider s390 and (x86/arm) KVM. Once we have a few, more can
> follow later, but I think its important to not only have PPC support for
> this.

Actually the s390 preemted check via sigp sense running  is available for
all hypervisors (z/VM, LPAR and KVM) which implies everywhere as you can no
longer buy s390 systems without LPAR.

As Heiko already pointed out we could simply use a small inline function
that calls cpu_is_preempted from arch/s390/lib/spinlock (or smp_vcpu_scheduled from smp.c)

Christian