linux-kernel - [PATCH 2/2] x86: fix platform info detection in frequency invariance

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Message-Id: <20220520161022.5972-2-ggherdovich@suse.cz>
Date:   Fri, 20 May 2022 18:10:22 +0200
From:   Giovanni Gherdovich <ggherdovich@...e.cz>
To:     Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Giovanni Gherdovich <ggherdovich@...e.cz>
Subject: [PATCH 2/2] x86: fix platform info detection in frequency invariance

Once the microarchitecture is recognized (via x86_match_cpu()), a failure
in setting base_freq/turbo_freq should result in bailing out from frequency
invariance, not in trying the next microarchitecture. This is because the
call to core_set_max_freq_ratio() isn't guarded by x86_match_cpu(). The
call to core_set_max_freq_ratio() should happen if no more specific
microarch matched, but not in case of prior errors.

Initializing base_freq=0 and turbo_freq=0 gives a mean for later code to
check if setup failed.

Fixes: db441bd9f630 ("x86, sched: Move check for CPU type to caller function")
Signed-off-by: Giovanni Gherdovich <ggherdovich@...e.cz>
---
 arch/x86/kernel/smpboot.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 225a3c31297c..d0a692ea8294 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -2044,23 +2044,26 @@ static bool core_set_max_freq_ratio(u64 *base_freq, u64 *turbo_freq)
 
 static bool intel_set_max_freq_ratio(void)
 {
-	u64 base_freq, turbo_freq;
+	u64 base_freq = 0, turbo_freq = 0;
 	u64 turbo_ratio;
 
 	if (slv_set_max_freq_ratio(&base_freq, &turbo_freq))
 		goto out;
 
-	if (x86_match_cpu(has_glm_turbo_ratio_limits) &&
-	    skx_set_max_freq_ratio(&base_freq, &turbo_freq, 1))
+	if (x86_match_cpu(has_glm_turbo_ratio_limits)) {
+		skx_set_max_freq_ratio(&base_freq, &turbo_freq, 1);
 		goto out;
+	}
 
-	if (x86_match_cpu(has_knl_turbo_ratio_limits) &&
-	    knl_set_max_freq_ratio(&base_freq, &turbo_freq, 1))
+	if (x86_match_cpu(has_knl_turbo_ratio_limits)) {
+		knl_set_max_freq_ratio(&base_freq, &turbo_freq, 1);
 		goto out;
+	}
 
-	if (x86_match_cpu(has_skx_turbo_ratio_limits) &&
-	    skx_set_max_freq_ratio(&base_freq, &turbo_freq, 4))
+	if (x86_match_cpu(has_skx_turbo_ratio_limits)) {
+		skx_set_max_freq_ratio(&base_freq, &turbo_freq, 4);
 		goto out;
+	}
 
 	if (core_set_max_freq_ratio(&base_freq, &turbo_freq))
 		goto out;
-- 
2.31.1