From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D514AC2BA18 for ; Tue, 18 Jun 2024 12:46:58 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.743050.1149927 (Exim 4.92) (envelope-from ) id 1sJYEN-0002vu-8m; Tue, 18 Jun 2024 12:46:35 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 743050.1149927; Tue, 18 Jun 2024 12:46:35 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1sJYEN-0002vn-4q; Tue, 18 Jun 2024 12:46:35 +0000 Received: by outflank-mailman (input) for mailman id 743050; Tue, 18 Jun 2024 12:46:34 +0000 Received: from se1-gles-flk1-in.inumbo.com ([94.247.172.50] helo=se1-gles-flk1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1sJYEM-0002vh-DP for xen-devel@lists.xenproject.org; Tue, 18 Jun 2024 12:46:34 +0000 Received: from mail-ot1-x332.google.com (mail-ot1-x332.google.com [2607:f8b0:4864:20::332]) by se1-gles-flk1.inumbo.com (Halon) with ESMTPS id c99451bf-2d70-11ef-b4bb-af5377834399; Tue, 18 Jun 2024 14:46:32 +0200 (CEST) Received: by mail-ot1-x332.google.com with SMTP id 46e09a7af769-6f98178ceb3so2951878a34.0 for ; Tue, 18 Jun 2024 05:46:32 -0700 (PDT) Received: from [10.125.226.166] ([160.101.139.1]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6b2a5eb4dc1sm65847196d6.100.2024.06.18.05.46.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Jun 2024 05:46:30 -0700 (PDT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: c99451bf-2d70-11ef-b4bb-af5377834399 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=google; t=1718714791; x=1719319591; darn=lists.xenproject.org; h=content-transfer-encoding:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:from:to:cc:subject:date:message-id:reply-to; bh=Q3inkv2VK9BTIRLUHw7TDus7E6YrNOM+cOrHUXeW0n0=; b=MfNCAygjlqcRtFqTlaAzRWbatrBilLsG3dEZxeeDA9ZC4/KYZ0VA10D1BbnGHWgQ4m aWT5VBmg1oNTBiujzvocooT7y7j1UGD1xVE6JjbXR4YPZvh9zFWYu6k86kkiLZBPdnIP sgPOy3UQacAwUNAGpbLxoiNtAoqSVlmNa5M38= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1718714791; x=1719319591; h=content-transfer-encoding:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Q3inkv2VK9BTIRLUHw7TDus7E6YrNOM+cOrHUXeW0n0=; b=SXNcVAoOVIMDHQu/tyD86O3xSVF4l0yxub1u04bmtU/UaBpbPWt82/mXTHwiSwg4TA n8cW1N+3bO2vhFVMtwGPrZ6sVjkQNopMMepMH4Q9/iWNsZvS0OvrXJOkYII/KBk+5c+0 bE3cnI3pwIENwITbJh22tYYe8iJzZVtYhoBpN8rQiVk5v8HAL7St3Ywr5Pn7wOnmfmf7 P5zooHxTWWs2w/HRLhclXBPpeMSgefClDPEkvrcnIkdS0dDGC3PQ2PWBEngKdG8H1q9N IyJcXUY3Rl3ilJTfvKOMUpIVF/Ps5DOS+TPEx/kkkxLmftSiDLlYfn6f59Yoi61czlSt pNsQ== X-Forwarded-Encrypted: i=1; AJvYcCVXHieeD6lYJrliikwlHK3P8qwdXR6NXDNMQZM63TgI+eQH+jtwpXScSOQLFpXBmWO2ldVGgwHR6zJ09u3EPApvK3dbzRUrI4xuWe4Yggg= X-Gm-Message-State: AOJu0Yze8AaDN2Vz5iaxPQE4xmpbNm0HR/sr2ng6Z4UYg9NHo4A25PEl ORO5YmMUmv0L/hebxxnoawq/36gE65gA/BstRsafx7AumYwdqTtdQnEqpJpyTLU= X-Google-Smtp-Source: AGHT+IEkKpl7JK/kqiyPl56NU53+vw7BNCCoorwn1aek/kN8SdxFdptHiz8mzmGwr2qQNcrYO795SA== X-Received: by 2002:a05:6830:3495:b0:6fc:3491:877 with SMTP id 46e09a7af769-6fc34910b59mr10570275a34.26.1718714790668; Tue, 18 Jun 2024 05:46:30 -0700 (PDT) Message-ID: <9d43b148-2cb6-45c8-a84c-0e51219669fa@citrix.com> Date: Tue, 18 Jun 2024 13:46:28 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH for 4.19?] x86/Intel: unlock CPUID earlier for the BSP To: Jan Beulich Cc: =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Oleksii Kurochko , "xen-devel@lists.xenproject.org" References: <82277592-ea96-47c8-a991-7afd97d7a7bc@suse.com> <8fb21b45-c803-4d37-8df8-3a1afa677ef7@citrix.com> Content-Language: en-GB From: Andrew Cooper Autocrypt: addr=andrew.cooper3@citrix.com; keydata= xsFNBFLhNn8BEADVhE+Hb8i0GV6mihnnr/uiQQdPF8kUoFzCOPXkf7jQ5sLYeJa0cQi6Penp VtiFYznTairnVsN5J+ujSTIb+OlMSJUWV4opS7WVNnxHbFTPYZVQ3erv7NKc2iVizCRZ2Kxn srM1oPXWRic8BIAdYOKOloF2300SL/bIpeD+x7h3w9B/qez7nOin5NzkxgFoaUeIal12pXSR Q354FKFoy6Vh96gc4VRqte3jw8mPuJQpfws+Pb+swvSf/i1q1+1I4jsRQQh2m6OTADHIqg2E ofTYAEh7R5HfPx0EXoEDMdRjOeKn8+vvkAwhviWXTHlG3R1QkbE5M/oywnZ83udJmi+lxjJ5 YhQ5IzomvJ16H0Bq+TLyVLO/VRksp1VR9HxCzItLNCS8PdpYYz5TC204ViycobYU65WMpzWe LFAGn8jSS25XIpqv0Y9k87dLbctKKA14Ifw2kq5OIVu2FuX+3i446JOa2vpCI9GcjCzi3oHV e00bzYiHMIl0FICrNJU0Kjho8pdo0m2uxkn6SYEpogAy9pnatUlO+erL4LqFUO7GXSdBRbw5 gNt25XTLdSFuZtMxkY3tq8MFss5QnjhehCVPEpE6y9ZjI4XB8ad1G4oBHVGK5LMsvg22PfMJ ISWFSHoF/B5+lHkCKWkFxZ0gZn33ju5n6/FOdEx4B8cMJt+cWwARAQABzSlBbmRyZXcgQ29v cGVyIDxhbmRyZXcuY29vcGVyM0BjaXRyaXguY29tPsLBegQTAQgAJAIbAwULCQgHAwUVCgkI CwUWAgMBAAIeAQIXgAUCWKD95wIZAQAKCRBlw/kGpdefoHbdD/9AIoR3k6fKl+RFiFpyAhvO 59ttDFI7nIAnlYngev2XUR3acFElJATHSDO0ju+hqWqAb8kVijXLops0gOfqt3VPZq9cuHlh IMDquatGLzAadfFx2eQYIYT+FYuMoPZy/aTUazmJIDVxP7L383grjIkn+7tAv+qeDfE+txL4 SAm1UHNvmdfgL2/lcmL3xRh7sub3nJilM93RWX1Pe5LBSDXO45uzCGEdst6uSlzYR/MEr+5Z JQQ32JV64zwvf/aKaagSQSQMYNX9JFgfZ3TKWC1KJQbX5ssoX/5hNLqxMcZV3TN7kU8I3kjK mPec9+1nECOjjJSO/h4P0sBZyIUGfguwzhEeGf4sMCuSEM4xjCnwiBwftR17sr0spYcOpqET ZGcAmyYcNjy6CYadNCnfR40vhhWuCfNCBzWnUW0lFoo12wb0YnzoOLjvfD6OL3JjIUJNOmJy RCsJ5IA/Iz33RhSVRmROu+TztwuThClw63g7+hoyewv7BemKyuU6FTVhjjW+XUWmS/FzknSi dAG+insr0746cTPpSkGl3KAXeWDGJzve7/SBBfyznWCMGaf8E2P1oOdIZRxHgWj0zNr1+ooF /PzgLPiCI4OMUttTlEKChgbUTQ+5o0P080JojqfXwbPAyumbaYcQNiH1/xYbJdOFSiBv9rpt TQTBLzDKXok86M7BTQRS4TZ/ARAAkgqudHsp+hd82UVkvgnlqZjzz2vyrYfz7bkPtXaGb9H4 Rfo7mQsEQavEBdWWjbga6eMnDqtu+FC+qeTGYebToxEyp2lKDSoAsvt8w82tIlP/EbmRbDVn 7bhjBlfRcFjVYw8uVDPptT0TV47vpoCVkTwcyb6OltJrvg/QzV9f07DJswuda1JH3/qvYu0p vjPnYvCq4NsqY2XSdAJ02HrdYPFtNyPEntu1n1KK+gJrstjtw7KsZ4ygXYrsm/oCBiVW/OgU g/XIlGErkrxe4vQvJyVwg6YH653YTX5hLLUEL1NS4TCo47RP+wi6y+TnuAL36UtK/uFyEuPy wwrDVcC4cIFhYSfsO0BumEI65yu7a8aHbGfq2lW251UcoU48Z27ZUUZd2Dr6O/n8poQHbaTd 6bJJSjzGGHZVbRP9UQ3lkmkmc0+XCHmj5WhwNNYjgbbmML7y0fsJT5RgvefAIFfHBg7fTY/i kBEimoUsTEQz+N4hbKwo1hULfVxDJStE4sbPhjbsPCrlXf6W9CxSyQ0qmZ2bXsLQYRj2xqd1 bpA+1o1j2N4/au1R/uSiUFjewJdT/LX1EklKDcQwpk06Af/N7VZtSfEJeRV04unbsKVXWZAk uAJyDDKN99ziC0Wz5kcPyVD1HNf8bgaqGDzrv3TfYjwqayRFcMf7xJaL9xXedMcAEQEAAcLB XwQYAQgACQUCUuE2fwIbDAAKCRBlw/kGpdefoG4XEACD1Qf/er8EA7g23HMxYWd3FXHThrVQ HgiGdk5Yh632vjOm9L4sd/GCEACVQKjsu98e8o3ysitFlznEns5EAAXEbITrgKWXDDUWGYxd pnjj2u+GkVdsOAGk0kxczX6s+VRBhpbBI2PWnOsRJgU2n10PZ3mZD4Xu9kU2IXYmuW+e5KCA vTArRUdCrAtIa1k01sPipPPw6dfxx2e5asy21YOytzxuWFfJTGnVxZZSCyLUO83sh6OZhJkk b9rxL9wPmpN/t2IPaEKoAc0FTQZS36wAMOXkBh24PQ9gaLJvfPKpNzGD8XWR5HHF0NLIJhgg 4ZlEXQ2fVp3XrtocHqhu4UZR4koCijgB8sB7Tb0GCpwK+C4UePdFLfhKyRdSXuvY3AHJd4CP 4JzW0Bzq/WXY3XMOzUTYApGQpnUpdOmuQSfpV9MQO+/jo7r6yPbxT7CwRS5dcQPzUiuHLK9i nvjREdh84qycnx0/6dDroYhp0DFv4udxuAvt1h4wGwTPRQZerSm4xaYegEFusyhbZrI0U9tJ B8WrhBLXDiYlyJT6zOV2yZFuW47VrLsjYnHwn27hmxTC/7tvG3euCklmkn9Sl9IAKFu29RSo d5bD8kMSCYsTqtTfT6W4A3qHGvIDta3ptLYpIAOD2sY3GYq2nf3Bbzx81wZK14JdDDHUX2Rs 6+ahAA== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 14/06/2024 12:12 pm, Jan Beulich wrote: > On 14.06.2024 12:14, Andrew Cooper wrote: >> On 14/06/2024 7:27 am, Jan Beulich wrote: >>> On 13.06.2024 18:17, Andrew Cooper wrote: >>>> On 13/06/2024 9:19 am, Jan Beulich wrote: >>>>> Intel CPUs have a MSR bit to limit CPUID enumeration to leaf two. If >>>>> this bit is set by the BIOS then CPUID evaluation does not work when >>>>> data from any leaf greater than two is needed; early_cpu_init() in >>>>> particular wants to collect leaf 7 data. >>>>> >>>>> Cure this by unlocking CPUID right before evaluating anything which >>>>> depends on the maximum CPUID leaf being greater than two. >>>>> >>>>> Inspired by (and description cloned from) Linux commit 0c2f6d04619e >>>>> ("x86/topology/intel: Unlock CPUID before evaluating anything"). >>>>> >>>>> Signed-off-by: Jan Beulich >>>>> --- >>>>> While I couldn't spot anything, it kind of feels as if I'm overlooking >>>>> further places where we might be inspecting in particular leaf 7 yet >>>>> earlier. >>>>> >>>>> No Fixes: tag(s), as imo it would be too many that would want >>>>> enumerating. >>>> I also saw that go by, but concluded that Xen doesn't need it, hence why >>>> I left it alone. >>>> >>>> The truth is that only the BSP needs it.  APs sort it out in the >>>> trampoline via trampoline_misc_enable_off, because they need to clear >>>> XD_DISABLE in prior to enabling paging, so we should be taking it out of >>>> early_init_intel(). >>> Except for the (odd) case also mentioned to Roger, where the BSP might have >>> the bit clear but some (or all) AP(s) have it set. >> Fine I suppose.  It's a single MSR adjustment once per CPU. >> >>>> But, we don't have an early BSP-only early hook, and I'm not overwhelmed >>>> at the idea of exporting it from intel.c >>>> >>>> I was intending to leave it alone until I can burn this whole >>>> infrastructure to the ground and make it work nicely with policies, but >>>> that's not a job for this point in the release... >>> This last part reads like the rest of your reply isn't an objection to me >>> putting this in with Roger's R-b, but it would be nice if you could >>> confirm this understanding of mine. Without this last part it, especially >>> the 2nd from last paragraph, certainly reads a little like an objection. >> I'm -1 to this generally.  It's churn without fixing anything AFAICT, > How that? We clearly do the adjustment too late right now for the BSP. > All the leaf-7 stuff added to early_cpu_init() (iirc in part in the course > of speculation work) is useless on a system where firmware set that flag. After discussing this at the x86 maintainers meeting, I agree that it is fixing a potential bug. So, while I really dislike the patch, it's the right approach in the short term, and should go in. ~Andrew