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 EA1AB32E73E for ; Wed, 15 Oct 2025 15:41:28 +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=1760542890; cv=none; b=VacbS57N/9nXEu+5q0fSvaSKaQDBTSEFGCtEuu3qY75bgCJgp9q5DokRpAuXQGTB3KvzHjDo+IKYTG6nofZcSOxm6r7HNTyGlW6QYfKoSMlXOap7ywTUhl3HNYgI7/70mpBoEzSa+tlDv+ABC8mn8UC4vY608HP5S8hhBoZ6+Vs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760542890; c=relaxed/simple; bh=D6ezY1oWIpf8BqRc7yZfx4KemYO4s7sx6SYcChN90Cg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=BL3+GcL8hdnWvkIjW3uf2niaEq/FmREe1Cjk+05E7fQuKqqyWva1FdOZQ62w/ZfQly4zI1P2J7SeCcmhfsC068kkDlHk+OD4WVYtvtFKZnB2f7mFqb0fc81oDGgBF30aJyBcKg87nuBMQozyVYB76MqEZv+JOKUVL00etc8cpEU= 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=hCajvFSD; 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="hCajvFSD" Received: from [192.168.72.64] ([218.1.208.81]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 59FFf4C72525831 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Wed, 15 Oct 2025 08:41:07 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 59FFf4C72525831 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025092201; t=1760542870; bh=D2DIl1u3eOZCQBBDyCfPopDmePcuHUKoOfEwvRnmPwc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=hCajvFSDAUZO1vocFzsYvuz1rbhB77kJC69FiIE53ob57GrDbR3y45nL/6xP7GGP4 v/yYFrTka7cS9LR2ZARiUaqPeg41tcMFabL9z0ZUiJ1AcOjtOxBMwSltrNeyLGP9mM v6INYPEjQRt737HSb7wkoNcVVHnaWdlfV134PtgMpSDXyutMhmp2gOUzvjyMawX5XV HjrnJ5wRP22w7LFgPZ+uLlOl8MBOk0nmAaDb8Fl5YSMoUqbR0juSCTpF60Hgkj4r5R 3t/Nz8ZkCr4v5BalaJWdjIhxjprGQ2Su2zkTsoxMqpIkpZRAwDU6l/8891VaQByPYI KJH7zRWaARHOg== Message-ID: <530c3c1a-5fab-4798-830b-1fe0e8522bc9@zytor.com> Date: Wed, 15 Oct 2025 23:41:03 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/cpufeatures: Correct LKGS feature flag description To: "H. Peter Anvin" , Borislav Petkov , Xin Li Cc: X86 ML , LKML , "Borislav Petkov (AMD)" References: <20251015103548.10194-1-bp@kernel.org> <2dd4dbee-dc7d-4118-be6d-94bd6d0d5030@zytor.com> <329BCA65-5152-4892-AFEA-DF72DCCE80B6@zytor.com> Content-Language: en-US From: Xin Li 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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/15/2025 11:36 PM, H. Peter Anvin wrote: > On October 15, 2025 8:34:00 AM PDT, Xin Li wrote: >> On 10/15/2025 11:18 PM, H. Peter Anvin wrote: >>> On October 15, 2025 8:08:17 AM PDT, Xin Li wrote: >>>> On 10/15/2025 6:35 PM, Borislav Petkov wrote: >>>>> From: "Borislav Petkov (AMD)" >>>>> >>>>> Quotation marks in cpufeatures.h comments are special and when the >>>>> comment begins with a quoted string, that string lands in /proc/cpuinfo, >>>>> turning it into a user-visible one. >>>>> >>>>> The LKGS comment doesn't begin with a quoted string but just in case >>>>> drop the quoted "kernel" in there to avoid confusion. And while at it, >>>>> simply change the description into what the LKGS instruction does for >>>>> more clarity. >>>>> >>>>> No functional changes. >>>>> >>>>> Signed-off-by: Borislav Petkov (AMD) >>>>> --- >>>>> arch/x86/include/asm/cpufeatures.h | 2 +- >>>>> tools/arch/x86/include/asm/cpufeatures.h | 2 +- >>>>> 2 files changed, 2 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h >>>>> index 80b68f4726e7..4fb5e12dbdbf 100644 >>>>> --- a/arch/x86/include/asm/cpufeatures.h >>>>> +++ b/arch/x86/include/asm/cpufeatures.h >>>>> @@ -320,7 +320,7 @@ >>>>> #define X86_FEATURE_FSRS (12*32+11) /* Fast short REP STOSB */ >>>>> #define X86_FEATURE_FSRC (12*32+12) /* Fast short REP {CMPSB,SCASB} */ >>>>> #define X86_FEATURE_FRED (12*32+17) /* "fred" Flexible Return and Event Delivery */ >>>>> -#define X86_FEATURE_LKGS (12*32+18) /* Load "kernel" (userspace) GS */ >>>>> +#define X86_FEATURE_LKGS (12*32+18) /* MSR_KERNEL_GS_BASE = GS.base */ >>>> >>>> Yes, the assignment is more clearer to us programmers. >>>> >>>> I'm just not sure if "correct" in the shortlog is accurate; it sounds the >>>> existing one is wrong. Otherwise, >>>> >>>> Reviewed-by: Xin Li (Intel) >>>> >>> >>> That "assignment" is rather wrong, though; it implies that the two are identical, which they are not; nor does it imply the relationship is fixed (that is provided by FRED, not LKGS). Perhaps just call it "Load user space GS". >> >> I see your point, is the following assignment better? >> >> MSR_KERNEL_GS_BASE = gs_sel->base >> > > Except that that is also wrong, because that's not all of what the instruction does. "Load user space GS" is really what it does, despite the initiate historical naming. > Do you mean the load of GS attributes by LKGS is still missing?