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

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Message-ID: <20160929103133.GW5016@twins.programming.kicks-ass.net>
Date:   Thu, 29 Sep 2016 12:31:33 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Christian Borntraeger <borntraeger@...ibm.com>
Cc:     Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>,
        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,
        Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH v3 0/4] implement vcpu preempted check

On Thu, Sep 29, 2016 at 12:23:19PM +0200, Christian Borntraeger wrote:
> 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)

Sure, and I had vague memories of Heiko's email. This patch set however
completely fails to do that trivial hooking up.