From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 986B970815 for ; Thu, 21 Nov 2024 15:45:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732203921; cv=none; b=JArsUX3Yug6myhsMamD9yPPBNNrbCAeQFfqiCOAi59SI7FzqCHV0ydVQoc2n7QI2qaGiQTnrqOHWGiHG4EVWTWP8oKfaJeSLC5K0bIRvYZ9RxItgH6tzP0MM/dR49+VwKGvec1OzDz3D2BSLQazHTxFRq3ZWW91MjLoqbaNT/qI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732203921; c=relaxed/simple; bh=C3+TMv+JfR89FLxkSrOyILwW0qfOXhqqT+YIQ09xJAg=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=oCULIwrAGt0wsDZnY4kaH7uW80YQz6SiHlbR6yXl6e2Vld/79LddFe7vtN/blXfDBfVs5HYP5HdBYQr8kRrKffsR9WWqVqnnsgDil3D9QeOfw++bRZQvPrDaoZPSqjaa0VveVix9Tu1S2/NOSZFaOtqm8d7+ltsjieheJjKHzds= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=wurPV7Fy; arc=none smtp.client-ip=209.85.128.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="wurPV7Fy" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-6eeb8aa2280so16173957b3.1 for ; Thu, 21 Nov 2024 07:45:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1732203918; x=1732808718; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=HamuaeYkSZPY6isgC3ltJNVU7ajwdcs8Gx9nQLciR8Y=; b=wurPV7FyJ2/tUS4coOTUPdrWg8M7xUGidzOPPYIeLPduJQqv2B3E11yP1VBD2PwLwY 0csMDREfdBaFWi1Jsv4OmZecsVVrjkN+xDMoeWXRwCZ69ohTDDPdNgTfqXnkzyiZ2okJ 0LSTH+8J6i/KEZmN1DffXQ6s4IoyvC9xs9XS7fKqLe+mp/pOfkc+fvta3nbhXyeFN9u4 Uk1cigsdrUD/mTJvEvoa6o5kgkFKP7y+3eRsUKZAv12P7tGr5q/jCczRq5khbIcbziDA 4/9y0spt40QaFWICkwzYHwkLak5dKg6Z0Q5/Zn3sXEs8OlxcXOTYDs7SD7Z0mcfrewNH M+pg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1732203918; x=1732808718; h=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=HamuaeYkSZPY6isgC3ltJNVU7ajwdcs8Gx9nQLciR8Y=; b=gct0/JYPAWTMV5rYxBew2pZubYm2SFkIn4BrGvxOyIRNgwEKh3GbMOVTa+fNyWlJ41 tCspYX3jqC5nf7Jn9Hwa8w8dV3UcOSfOloui0yvpoaT9lDneL84UcttlOZREPU5uvaNh ZqlrFmAGxyNRa/ng+p45WIU+wL4iYPa0YHI/dEBz9926cu/Ls/ZeYwFidOkP0cDO2b4Z 5icPwY6TLBMnQJxavpQjts+h5pP/LM4LdZTtt18jRxEaOM+EbuLxOuU+TEge1cCmYG8C CWv8wXrqajvdQsOmCbF1rWKP9R7YHGJN8Lo02/oWcCrAIrdv0gI00VeJpHOwysRt9fx2 wGyg== X-Gm-Message-State: AOJu0Yy+Xb6Lj50tAQS9OQ9cDA//MQyHMw8/piCcL7+tXUGwYacKrH/b iCbiI9s7CnPWwtg4ADIbi1UUqED9FLJHbG6iXbhs8XYjEAkYaHrgAOrbS1UKWJEii2OY8zpOPKB 5Qg== X-Google-Smtp-Source: AGHT+IFipUCBosSPRYKSM3o0GiYohdLjMf94GMG/BjwqRWrx5NmXMc/KFfYupFEzD8/S6jJX4iJYq/xKZnM= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:9d:3983:ac13:c240]) (user=seanjc job=sendgmr) by 2002:a05:690c:fcb:b0:6ea:1f5b:1f5e with SMTP id 00721157ae682-6eebd166cb4mr40747b3.4.1732203918448; Thu, 21 Nov 2024 07:45:18 -0800 (PST) Date: Thu, 21 Nov 2024 07:45:17 -0800 In-Reply-To: <20241120195340.047C9ABE@davehans-spike.ostc.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241120195327.26E06A69@davehans-spike.ostc.intel.com> <20241120195340.047C9ABE@davehans-spike.ostc.intel.com> Message-ID: Subject: Re: [PATCH 10/11] x86/fpu: Remove unnecessary CPUID level check From: Sean Christopherson To: Dave Hansen Cc: linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, bp@alien8.de, rafael@kernel.org, lenb@kernel.org, dave.jiang@intel.com, irenic.rajneesh@gmail.com, david.e.box@intel.com Content-Type: text/plain; charset="us-ascii" On Wed, Nov 20, 2024, Dave Hansen wrote: > > From: Dave Hansen > > The CPUID level dependency table will entirely zap X86_FEATURE_XSAVE What table is that? XSAVE depends on FXSR, but I can't find anything that clears X86_FEATURE_XSAVE if cpuid_level < XSTATE_CPUID. Even if it did, dropping a sanity check in a one-time path adds risk for almost no reward. > if the CPUID level is too low. This code is unreachable. Kill it. > > Signed-off-by: Dave Hansen > --- > > b/arch/x86/kernel/fpu/xstate.c | 5 ----- > 1 file changed, 5 deletions(-) > > diff -puN arch/x86/kernel/fpu/xstate.c~xsave-leaf-checks-2 arch/x86/kernel/fpu/xstate.c > --- a/arch/x86/kernel/fpu/xstate.c~xsave-leaf-checks-2 2024-11-20 11:44:20.369771244 -0800 > +++ b/arch/x86/kernel/fpu/xstate.c 2024-11-20 11:44:20.373771397 -0800 > @@ -764,11 +764,6 @@ void __init fpu__init_system_xstate(unsi > return; > } > > - if (boot_cpu_data.cpuid_level < XSTATE_CPUID) { > - WARN_ON_FPU(1); > - return; > - } > - > /* > * Find user xstates supported by the processor. > */ > _