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From: Giovanni Gherdovich <ggherdovich@suse.cz>
To: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Borislav Petkov <bp@suse.de>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>
Cc: x86@kernel.org, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Ricardo Neri <ricardo.neri-calderon@linux.intel.com>,
	Giovanni Gherdovich <ggherdovich@suse.cz>
Subject: [PATCH v2 2/3] x86, sched: Bail out of frequency invariance if turbo frequency is unknown
Date: Sun, 31 May 2020 20:24:52 +0200	[thread overview]
Message-ID: <20200531182453.15254-3-ggherdovich@suse.cz> (raw)
In-Reply-To: <20200531182453.15254-1-ggherdovich@suse.cz>

There may be CPUs that support turbo boost but don't declare any turbo
ratio, i.e. their MSR_TURBO_RATIO_LIMIT is all zeroes. In that condition
scale-invariant calculations can't be performed.

Signed-off-by: Giovanni Gherdovich <ggherdovich@suse.cz>
Suggested-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Fixes: 1567c3e3467c ("x86, sched: Add support for frequency invariance")
---
 arch/x86/kernel/smpboot.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index d660966d7de7..fe154c8226ba 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -2001,9 +2001,11 @@ static bool intel_set_max_freq_ratio(void)
 	/*
 	 * Some hypervisors advertise X86_FEATURE_APERFMPERF
 	 * but then fill all MSR's with zeroes.
+	 * Some CPUs have turbo boost but don't declare any turbo ratio
+	 * in MSR_TURBO_RATIO_LIMIT.
 	 */
-	if (!base_freq) {
-		pr_debug("Couldn't determine cpu base frequency, necessary for scale-invariant accounting.\n");
+	if (!base_freq || !turbo_freq) {
+		pr_debug("Couldn't determine cpu base or turbo frequency, necessary for scale-invariant accounting.\n");
 		return false;
 	}
 
-- 
2.16.4


  parent reply	other threads:[~2020-05-31 18:26 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-31 18:24 [PATCH v2 0/3] More frequency invariance fixes for x86 Giovanni Gherdovich
2020-05-31 18:24 ` [PATCH v2 1/3] x86, sched: check for counters overflow in frequency invariant accounting Giovanni Gherdovich
2020-06-03 14:22   ` Rafael J. Wysocki
2020-06-16 12:21   ` [tip: sched/core] " tip-bot2 for Giovanni Gherdovich
2020-10-22  8:46   ` [PATCH v2 1/3] " Peter Zijlstra
2020-10-22 12:21     ` Giovanni Gherdovich
2020-10-22 12:30       ` Peter Zijlstra
2020-05-31 18:24 ` Giovanni Gherdovich [this message]
2020-06-01 23:34   ` [PATCH v2 2/3] x86, sched: Bail out of frequency invariance if turbo frequency is unknown Ricardo Neri
2020-07-06 20:19     ` Ira Weiny
2020-06-03 14:23   ` Rafael J. Wysocki
2020-06-16 12:21   ` [tip: sched/core] " tip-bot2 for Giovanni Gherdovich
2020-05-31 18:24 ` [PATCH v2 3/3] x86, sched: Bail out of frequency invariance if turbo_freq/base_freq gives 0 Giovanni Gherdovich
2020-06-03 14:51   ` Rafael J. Wysocki
2020-06-16 12:21   ` [tip: sched/core] " tip-bot2 for Giovanni Gherdovich
2020-06-03 12:31 ` [PATCH v2 0/3] More frequency invariance fixes for x86 Peter Zijlstra

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