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Date:   Mon, 27 May 2019 14:32:06 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Juergen Gross <jgross@suse.com>, Nadav Amit <namit@vmware.com>,
        Ingo Molnar <mingo@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Borislav Petkov <bp@alien8.de>, linux-kernel@vger.kernel.org,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Sasha Levin <sashal@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, x86@kernel.org,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        linux-hyperv@vger.kernel.org,
        virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
        xen-devel@lists.xenproject.org
Subject: Re: [RFC PATCH 5/6] x86/mm/tlb: Flush remote and local TLBs
 concurrently
Message-ID: <20190527123206.GC2623@hirez.programming.kicks-ass.net>
References: <20190525082203.6531-1-namit@vmware.com>
 <20190525082203.6531-6-namit@vmware.com>
 <08b21fb5-2226-7924-30e3-31e4adcfc0a3@suse.com>
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On Mon, May 27, 2019 at 12:21:59PM +0200, Paolo Bonzini wrote:
> On 27/05/19 11:47, Peter Zijlstra wrote:

> > --- a/arch/x86/kernel/kvm.c
> > +++ b/arch/x86/kernel/kvm.c
> > @@ -580,7 +580,7 @@ static void __init kvm_apf_trap_init(voi
> >  
> >  static DEFINE_PER_CPU(cpumask_var_t, __pv_tlb_mask);
> >  
> > -static void kvm_flush_tlb_others(const struct cpumask *cpumask,
> > +static void kvm_flush_tlb_multi(const struct cpumask *cpumask,
> >  			const struct flush_tlb_info *info)
> >  {
> >  	u8 state;
> > @@ -594,6 +594,9 @@ static void kvm_flush_tlb_others(const s
> >  	 * queue flush_on_enter for pre-empted vCPUs
> >  	 */
> >  	for_each_cpu(cpu, flushmask) {
> > +		if (cpu == smp_processor_id())
> > +			continue;
> > +
> 
> Even this would be just an optimization; the vCPU you're running on
> cannot be preempted.  You can just change others to multi.

Yeah, I know, but it felt weird so I added the explicit skip. No strong
feelings though.