linux-kernel - Re: [PATCH v11 05/11] perf/x86: Keep LBR stack unchanged in host context for guest LBR event

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200518120205.GF277222@hirez.programming.kicks-ass.net>
Date:   Mon, 18 May 2020 14:02:05 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Like Xu <like.xu@...ux.intel.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>, ak@...ux.intel.com,
        wei.w.wang@...el.com
Subject: Re: [PATCH v11 05/11] perf/x86: Keep LBR stack unchanged in host
 context for guest LBR event

On Thu, May 14, 2020 at 04:30:48PM +0800, Like Xu wrote:
> @@ -544,7 +562,12 @@ void intel_pmu_lbr_enable_all(bool pmi)
>  {
>  	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
>  
> -	if (cpuc->lbr_users)
> +	/*
> +	 * When the LBR hardware is scheduled for a guest LBR event,
> +	 * the guest will dis/enables LBR itself at the appropriate time,
> +	 * including configuring MSR_LBR_SELECT.
> +	 */
> +	if (cpuc->lbr_users && !cpuc->guest_lbr_enabled)
>  		__intel_pmu_lbr_enable(pmi);
>  }

No!, that should be done through perf_event_attr::exclude_host, as I
believe all the other KVM event do it.