From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7F92E1A71F for ; Mon, 9 Oct 2023 16:29:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="2jRZ3KX0" Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C036D9E for ; Mon, 9 Oct 2023 09:29:52 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-5a507986ed6so82541547b3.1 for ; Mon, 09 Oct 2023 09:29:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1696868992; x=1697473792; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=rqY7KKcbXF3xUWGU4wT3dqp32k/36wxckx8YA28nXEY=; b=2jRZ3KX0B6IOGCxhNIVzbudTqLC/TNY8so4YAsUR7e2aLoZIPaCh7GssWxPmwwCO9t bS5qPjefeQcYibCCakz9dV+ZZHAKOqbV4qLtQn+c/klJyb/p7tUj/FM87VlD6YDFTsls ogn7NScS0YiE0/nFbdt3Ik2Y7b4NSfHAvGBPVEw5p9FCQf5xEo0iFxtUkw4ohpXFUENE +L956OtXXgljTFYVdB/uuIYoU16/m969JP4MxC6GWsR+0s57BCmJoedmUrWg3uSkY0ZW o5YlBNw9ByuTDMUAGQ2ufXeEKnNk09nuUUXxuP5s9wXXiD+q7tJJvjlTAyuC9C9SjVa8 hJWQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1696868992; x=1697473792; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=rqY7KKcbXF3xUWGU4wT3dqp32k/36wxckx8YA28nXEY=; b=qb3bzpSmbolptv5ssry5rVMdfRMMzfEWfMN4wBfbbCXSMgarjNUwgztB+lWUfDyZnV y1YqOWXtLZuVlpyHukhnMfsUFxTnv9SNhEqzoXqAZ1ubImiTwgdj8usAKC180EDl2axz VZBAMKwr39b61vTkD0AVd0jXBGtGaB2muUo9ICYSgqynerJVY1pEYXOick3DoknO5m01 07wnl2UQCocLBdAHiJ9nZFJBLlV3h3xq0F+fkEqu5RV8eTGhnO5GvrENxuTE6TQ3aXbV zAJ1pbYxQ/cqXpKLtH6KPTOVkLgGSo1H1Pkf7RivxDNlXMuC24meoQu0Mx9eazs/9y6c EhmQ== X-Gm-Message-State: AOJu0YzacgQtCZW8PdGvC65y0oJCotsOA4d4fBT9eSdK9a0bEFink4nX LSpEJOmLya17HvmfscSBygGxOomIyOQ= X-Google-Smtp-Source: AGHT+IFczvQ2UyFbt9J+8jf9SjSk/hCP3ruErRSBZVfUfVJwQHUAJnIuKo5VnY3DDHB7QaZzSZ3tTfpjOD8= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a81:ae26:0:b0:5a7:b8d1:ef65 with SMTP id m38-20020a81ae26000000b005a7b8d1ef65mr6581ywh.3.1696868991924; Mon, 09 Oct 2023 09:29:51 -0700 (PDT) Date: Mon, 9 Oct 2023 09:29:50 -0700 In-Reply-To: <20231007203411.GA8085@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231007203411.GA8085@noisy.programming.kicks-ass.net> Message-ID: Subject: Re: [PATCH] perf/x86/p4: Fix "Wunused-but-set-variable" warning From: Sean Christopherson To: Peter Zijlstra Cc: Lucy Mielke , mingo@redhat.com, acme@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, namhyung@kernel.org, irogers@google.com, adrian.hunter@intel.com, tglx@linutronix.de, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-9.6 required=5.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On Sat, Oct 07, 2023, Peter Zijlstra wrote: > On Sat, Oct 07, 2023 at 08:55:19PM +0200, Lucy Mielke wrote: > > This fixes a compiler warning when compiling an allyesconfig with W=3D1= : > > warning: variable =C2=B4high=C2=B4 set but not used [-Wunused-but-set-v= ariable] >=20 > What compiler and what .config? >=20 > > Signed-off-by: Lucy Mielke > > --- > > arch/x86/events/intel/p4.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > >=20 > > diff --git a/arch/x86/events/intel/p4.c b/arch/x86/events/intel/p4.c > > index 35936188db01..69aaf7c0f340 100644 > > --- a/arch/x86/events/intel/p4.c > > +++ b/arch/x86/events/intel/p4.c > > @@ -1366,7 +1366,7 @@ static __initconst const struct x86_pmu p4_pmu = =3D { > > =20 > > __init int p4_pmu_init(void) > > { > > - unsigned int low, high; > > + unsigned int low, __maybe_unused high; > > int i, reg; > > =20 > > /* If we get stripped -- indexing fails */ >=20 > Right after this we have: >=20 > rdmsr(MSR_IA32_MISC_ENABLE, low, high); >=20 > which should get high unconditionally used. If there's a problem then > it's probably inside that rdmsr macro. rdmsr() writes to "high", but nothing ever reads from high. FWIW, I would = _love_ for rdmsrl() to have return semantics, e.g. to be able to do: low =3D (u32)rdmsrl(MSR_IA32_MISC_ENABLE); or even if (!(rdmsrl(MSR_IA32_MISC_ENABLE) & BIT(7)))