linux-kernel - Re: cpu/hotplug: broken sibling thread hotplug

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Message-ID: <20190128143554.4e043691@redhat.com>
Date:   Mon, 28 Jan 2019 14:35:54 +0100
From:   Igor Mammedov <imammedo@...hat.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Joe Mario <jmario@...hat.com>, Jiri Kosina <jkosina@...e.cz>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org
Subject: Re: cpu/hotplug: broken sibling thread hotplug

On Mon, 28 Jan 2019 06:52:52 -0600
Josh Poimboeuf <jpoimboe@...hat.com> wrote:

> On Mon, Jan 28, 2019 at 11:13:04AM +0100, Igor Mammedov wrote:
> > On Fri, 25 Jan 2019 11:02:03 -0600
> > Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> >   
> > > On Fri, Jan 25, 2019 at 10:36:57AM -0600, Josh Poimboeuf wrote:  
> > > > How about this patch?  It's just a revert of 73d5e2b47264 and
> > > > bc2d8d262cba, plus the 1-line vmx_vm_init() change.  If it looks ok to
> > > > you, I can clean it up and submit an official version.    
> > > 
> > > This one actually compiles...  
> > 
> > Looks good to me,
> > (one small question below)
> > 
> >  
> > [...]  
> > >  static inline bool cpu_smt_allowed(unsigned int cpu)
> > >  {
> > > -	if (topology_is_primary_thread(cpu))
> > > +	if (cpu_smt_control == CPU_SMT_ENABLED)
> > >  		return true;
> > >  
> > > -	/*
> > > -	 * If the CPU is not a 'primary' thread and the booted_once bit is
> > > -	 * set then the processor has SMT support. Store this information
> > > -	 * for the late check of SMT support in cpu_smt_check_topology().
> > > -	 */
> > > -	if (per_cpu(cpuhp_state, cpu).booted_once)
> > > -		cpu_smt_available = true;
> > > -
> > > -	if (cpu_smt_control == CPU_SMT_ENABLED)
> > > +	if (topology_is_primary_thread(cpu))
> > >  		return true;  
> > why did you swap cpu_smt_control and topology_is_primary_thread checks?  
> 
> That's just the revert of bc2d8d262cba5.
ok. waiting for formal patch
pls, CC kvm@...r.kernel.org so Paolo could have a chance to review
(pick it up if Thomas is ok with approach)