linux-kernel - Re: [PATCH] x86/hyperv: Disable preemption while setting reenlightenment vector

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Message-ID: <877e9o7a4e.fsf@vitty.brq.redhat.com>
Date:   Fri, 14 Jun 2019 12:08:01 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Dmitry Safonov <dima@...sta.com>, linux-kernel@...r.kernel.org,
        Prasanna Panchamukhi <panchamukhi@...sta.com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Cathy Avery <cavery@...hat.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        "Michael Kelley \(EOSG\)" <Michael.H.Kelley@...rosoft.com>,
        Mohammed Gamal <mmorsy@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Roman Kagan <rkagan@...tuozzo.com>,
        Sasha Levin <sashal@...nel.org>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        devel@...uxdriverproject.org, kvm@...r.kernel.org,
        linux-hyperv@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] x86/hyperv: Disable preemption while setting reenlightenment vector

Peter Zijlstra <peterz@...radead.org> writes:

> @@ -182,7 +182,7 @@ void set_hv_tscchange_cb(void (*cb)(void))
>  	struct hv_reenlightenment_control re_ctrl = {
>  		.vector = HYPERV_REENLIGHTENMENT_VECTOR,
>  		.enabled = 1,
> -		.target_vp = hv_vp_index[smp_processor_id()]
> +		.target_vp = hv_vp_index[raw_smp_processor_id()]
>  	};
>  	struct hv_tsc_emulation_control emu_ctrl = {.enabled = 1};
>  

Yes, this should do, thanks! I'd also suggest to leave a comment like
	/* 
         * This function can get preemted and migrate to a different CPU
	 * but this doesn't matter. We just need to assign
	 * reenlightenment notification to some online CPU. In case this
         * CPU goes offline, hv_cpu_die() will re-assign it to some
 	 * other online CPU.
	 */
  
-- 
Vitaly