linux-kernel - Re: [PATCH V2] cpufreq: Call transition notifier only once for each policy

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: <20190319055044.xbxr6ph5hl4zcucb@vireshk-i7>
Date:   Tue, 19 Mar 2019 11:20:44 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        sparclinux@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH V2] cpufreq: Call transition notifier only once for each
 policy

On 18-03-19, 12:49, Rafael J. Wysocki wrote:
> To summarize, I think that it would be sufficient to do this just for
> policy->cpu and, as Peter said, warn once if there are more CPUs in
> the policy or policy->cpu is not the CPU running this code.  And mark
> the TSC as unstable in both of these cases.

How about this ?

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 3fae23834069..4d3681cfb6e0 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -958,10 +958,13 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
        struct cpufreq_freqs *freq = data;
        unsigned long *lpj;
 
+       if (WARN_ON_ONCE(cpumask_weight(freq->policy->related_cpus) != 1))
+               mark_tsc_unstable("cpufreq policy has more than CPU");
+
        lpj = &boot_cpu_data.loops_per_jiffy;
 #ifdef CONFIG_SMP
        if (!(freq->flags & CPUFREQ_CONST_LOOPS))
-               lpj = &cpu_data(freq->cpu).loops_per_jiffy;
+               lpj = &cpu_data(freq->policy->cpu).loops_per_jiffy;
 #endif
 
        if (!ref_freq) {
@@ -977,7 +980,7 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
                if (!(freq->flags & CPUFREQ_CONST_LOOPS))
                        mark_tsc_unstable("cpufreq changes");
 
-               set_cyc2ns_scale(tsc_khz, freq->cpu, rdtsc());
+               set_cyc2ns_scale(tsc_khz, freq->policy->cpu, rdtsc());
        }
 
        return 0;