From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (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 8E8552236E8 for ; Tue, 22 Jul 2025 09:08:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753175340; cv=none; b=MzX/s+/UQF7ZuySyF3ycmPrDH0UBx/nKqmdWKasib97q3V8yLXZCpKoNXZoouCpFdGffGYJbCwnljqBCoA3nrVUvv0PgmpszUQciZQjt8pI+/dt/YA0/7Wo0POMm1exUT+nGnRROmlNO14Aqy/5EHVmKvug02siae/fHbe4ROXs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753175340; c=relaxed/simple; bh=7g5TcZqhFRX/me+tMxGLZKo7fKEWw70YL4VjZOwSd14=; h=Message-ID:Date:MIME-Version:From:Subject:To:Cc:References: In-Reply-To:Content-Type; b=Vkh5GI+UETiPr3wO1Hvwe4h+W2BzMvT0Py9pAUTJd9gWNB1ZAeg0BXX2Omt0xV20tzUFQdbxOr3M+8pMoEASUTkKZp/AdAeigsMIoWuzdMTRqgb2rjRU/Y8XMhm5VPvEfQhEjf9jmPb+p1H3SwzA5j25btX5qBTmyGn3tEZqCLQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=NJ1dF+vU; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="NJ1dF+vU" Received: from [192.168.7.202] ([71.202.166.45]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 56M98SmG471807 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Tue, 22 Jul 2025 02:08:29 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 56M98SmG471807 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025062101; t=1753175309; bh=YHKVV5kv5jsDqdQJolZk/Edn0dtS4CBCeXZ06HoXdVE=; h=Date:From:Subject:To:Cc:References:In-Reply-To:From; b=NJ1dF+vUpUXHm+oa8IwUsr4GP3wgwt1hQPB1ZiV0yzJ5ZhqYRToRD9JGq+RMV0ng3 anwanqaOLKQtt/zwLyfdC8eOranJG+qPW4j48MoFsLAXgcORcfOMtrKuOWmARilbUv DuQvAPwglcNQgFS1G3OfNpEBc7HEbEYeKv12jpWoNmbxCuIZAh8V9KmsXaAtw4KZV1 ak2EqBR5oltb87B5VFYWiYutL9cWSV+OutsiLQg1QBckyu9V+Bm7K3DGihFLgmPYGH BX6Yb90CwpyH/FAG6i4Vr56ZcPDEj7uRWq4kyGpV4GtRZ28mAqthef3sgDP8/frtR0 fbyUoLMUmu7yA== Message-ID: <32382f60-79fb-4cfa-87b4-581f92c980da@zytor.com> Date: Tue, 22 Jul 2025 02:08:28 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Xin Li Subject: Re: [PATCH] x86: Clear LAM and FRED feature bits To: Wieczor-Retman Maciej Cc: Gleixner Thomas , Molnar Ingo , Petkov Borislav , Hansen Dave , x86@kernel.org, "Anvin H. Peter" , linux-kernel@vger.kernel.org References: <20250722074439.4069992-1-maciej.wieczor-retman@intel.com> Content-Language: en-US Autocrypt: addr=xin@zytor.com; keydata= xsDNBGUPz1cBDACS/9yOJGojBFPxFt0OfTWuMl0uSgpwk37uRrFPTTLw4BaxhlFL0bjs6q+0 2OfG34R+a0ZCuj5c9vggUMoOLdDyA7yPVAJU0OX6lqpg6z/kyQg3t4jvajG6aCgwSDx5Kzg5 Rj3AXl8k2wb0jdqRB4RvaOPFiHNGgXCs5Pkux/qr0laeFIpzMKMootGa4kfURgPhRzUaM1vy bsMsL8vpJtGUmitrSqe5dVNBH00whLtPFM7IbzKURPUOkRRiusFAsw0a1ztCgoFczq6VfAVu raTye0L/VXwZd+aGi401V2tLsAHxxckRi9p3mc0jExPc60joK+aZPy6amwSCy5kAJ/AboYtY VmKIGKx1yx8POy6m+1lZ8C0q9b8eJ8kWPAR78PgT37FQWKYS1uAroG2wLdK7FiIEpPhCD+zH wlslo2ETbdKjrLIPNehQCOWrT32k8vFNEMLP5G/mmjfNj5sEf3IOKgMTMVl9AFjsINLHcxEQ 6T8nGbX/n3msP6A36FDfdSEAEQEAAc0WWGluIExpIDx4aW5Aenl0b3IuY29tPsLBDQQTAQgA NxYhBIUq/WFSDTiOvUIqv2u9DlcdrjdRBQJlD89XBQkFo5qAAhsDBAsJCAcFFQgJCgsFFgID AQAACgkQa70OVx2uN1HUpgv/cM2fsFCQodLArMTX5nt9yqAWgA5t1srri6EgS8W3F+3Kitge tYTBKu6j5BXuXaX3vyfCm+zajDJN77JHuYnpcKKr13VcZi1Swv6Jx1u0II8DOmoDYLb1Q2ZW v83W55fOWJ2g72x/UjVJBQ0sVjAngazU3ckc0TeNQlkcpSVGa/qBIHLfZraWtdrNAQT4A1fa sWGuJrChBFhtKbYXbUCu9AoYmmbQnsx2EWoJy3h7OjtfFapJbPZql+no5AJ3Mk9eE5oWyLH+ QWqtOeJM7kKvn/dBudokFSNhDUw06e7EoVPSJyUIMbYtUO7g2+Atu44G/EPP0yV0J4lRO6EA wYRXff7+I1jIWEHpj5EFVYO6SmBg7zF2illHEW31JAPtdDLDHYcZDfS41caEKOQIPsdzQkaQ oW2hchcjcMPAfyhhRzUpVHLPxLCetP8vrVhTvnaZUo0xaVYb3+wjP+D5j/3+hwblu2agPsaE vgVbZ8Fx3TUxUPCAdr/p73DGg57oHjgezsDNBGUPz1gBDAD4Mg7hMFRQqlzotcNSxatlAQNL MadLfUTFz8wUUa21LPLrHBkUwm8RujehJrzcVbPYwPXIO0uyL/F///CogMNx7Iwo6by43KOy g89wVFhyy237EY76j1lVfLzcMYmjBoTH95fJC/lVb5Whxil6KjSN/R/y3jfG1dPXfwAuZ/4N cMoOslWkfZKJeEut5aZTRepKKF54T5r49H9F7OFLyxrC/uI9UDttWqMxcWyCkHh0v1Di8176 jjYRNTrGEfYfGxSp+3jYL3PoNceIMkqM9haXjjGl0W1B4BidK1LVYBNov0rTEzyr0a1riUrp Qk+6z/LHxCM9lFFXnqH7KWeToTOPQebD2B/Ah5CZlft41i8L6LOF/LCuDBuYlu/fI2nuCc8d m4wwtkou1Y/kIwbEsE/6RQwRXUZhzO6llfoN96Fczr/RwvPIK5SVMixqWq4QGFAyK0m/1ap4 bhIRrdCLVQcgU4glo17vqfEaRcTW5SgX+pGs4KIPPBE5J/ABD6pBnUUAEQEAAcLA/AQYAQgA JhYhBIUq/WFSDTiOvUIqv2u9DlcdrjdRBQJlD89ZBQkFo5qAAhsMAAoJEGu9DlcdrjdR4C0L /RcjolEjoZW8VsyxWtXazQPnaRvzZ4vhmGOsCPr2BPtMlSwDzTlri8BBG1/3t/DNK4JLuwEj OAIE3fkkm+UG4Kjud6aNeraDI52DRVCSx6xff3bjmJsJJMb12mWglN6LjdF6K+PE+OTJUh2F dOhslN5C2kgl0dvUuevwMgQF3IljLmi/6APKYJHjkJpu1E6luZec/lRbetHuNFtbh3xgFIJx 2RpgVDP4xB3f8r0I+y6ua+p7fgOjDLyoFjubRGed0Be45JJQEn7A3CSb6Xu7NYobnxfkwAGZ Q81a2XtvNS7Aj6NWVoOQB5KbM4yosO5+Me1V1SkX2jlnn26JPEvbV3KRFcwV5RnDxm4OQTSk PYbAkjBbm+tuJ/Sm+5Yp5T/BnKz21FoCS8uvTiziHj2H7Cuekn6F8EYhegONm+RVg3vikOpn gao85i4HwQTK9/D1wgJIQkdwWXVMZ6q/OALaBp82vQ2U9sjTyFXgDjglgh00VRAHP7u1Rcu4 l75w1xInsg== In-Reply-To: <20250722074439.4069992-1-maciej.wieczor-retman@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit > On Jul 22, 2025, at 12:54 AM, Maciej Wieczor-Retman wrote: > > If LAM (CONFIG_ADDRESS_MASKING) or FRED (CONFIG_X86_FRED) are disabled > during compile time, they still are enumerated in macros such as > cpu_has() or this_cpu_has() that use the x86_capability bitmask. The > features are also visible in /proc/cpuinfo even though they are not > enabled - which is contrary to what the documentation states about the > file. I'm curious how this bug is introduced with my patch set that adds the AWK script which automatically generates the CPU feature mask header. > > The documentation for x86/cpuinfo.rst also states how to handle features > disabled at compile time: > > The kernel disabled support for it at compile-time > -------------------------------------------------- > > For example, if Linear Address Masking (LAM) is not enabled when > building (i.e., CONFIG_ADDRESS_MASKING is not selected) the flag > "lam" will not show up. Even though the feature will still be > detected via CPUID, the kernel disables it by clearing via > setup_clear_cpu_cap(X86_FEATURE_LAM). > > Clear feature bits if they are present in the DISABLED_MASK. > > Signed-off-by: Maciej Wieczor-Retman And we need a Fixes tag and CC stable. > --- > arch/x86/kernel/cpu/common.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c > index 77afca95cced..1c5af795cedc 100644 > --- a/arch/x86/kernel/cpu/common.c > +++ b/arch/x86/kernel/cpu/common.c > @@ -1782,6 +1782,16 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) > if (!pgtable_l5_enabled()) > setup_clear_cpu_cap(X86_FEATURE_LA57); > > + /* > + * If a feature is disabled during compile time clear its feature > + * bit to prevent it from showing up in the x86_capability bitmask. > + */ > + if (!cpu_feature_enabled(X86_FEATURE_LAM)) > + setup_clear_cpu_cap(X86_FEATURE_LAM); > + > + if (!cpu_feature_enabled(X86_FEATURE_FRED)) > + setup_clear_cpu_cap(X86_FEATURE_FRED); > + The following code will work as a generic fix: c->x86_capability[i] &= ~DISABLED_MASK(i); And DISABLED_MASK(x) needs to be defined like DISABLED_MASK_BIT_SET(x). Thanks! Xin