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 9452DC25B4F for ; Tue, 7 May 2024 12:20:21 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.718045.1120542 (Exim 4.92) (envelope-from ) id 1s4Jnh-0007Ii-Bl; Tue, 07 May 2024 12:20:05 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 718045.1120542; Tue, 07 May 2024 12:20:05 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1s4Jnh-0007IA-8z; Tue, 07 May 2024 12:20:05 +0000 Received: by outflank-mailman (input) for mailman id 718045; Tue, 07 May 2024 12:20:04 +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 1s4Jng-0006yi-3S for xen-devel@lists.xenproject.org; Tue, 07 May 2024 12:20:04 +0000 Received: from mail-qk1-x732.google.com (mail-qk1-x732.google.com [2607:f8b0:4864:20::732]) by se1-gles-flk1.inumbo.com (Halon) with ESMTPS id 1fc869c9-0c6c-11ef-b4bb-af5377834399; Tue, 07 May 2024 14:20:00 +0200 (CEST) Received: by mail-qk1-x732.google.com with SMTP id af79cd13be357-7928c5cb63fso215047585a.1 for ; Tue, 07 May 2024 05:20:01 -0700 (PDT) Received: from [10.80.67.140] (default-46-102-197-194.interdsl.co.uk. [46.102.197.194]) by smtp.gmail.com with ESMTPSA id n22-20020ae9c316000000b007925fc27b1bsm4839542qkg.124.2024.05.07.05.19.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 May 2024 05:20:00 -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: 1fc869c9-0c6c-11ef-b4bb-af5377834399 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=google; t=1715084400; x=1715689200; 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=YRLVjkv17D9aBha14p2zSizQpD/IHwVWplpoCtaVJyk=; b=lbtJLP9NOOAhnd9uPi5BBvje7I7omfk4HJcUV0z782deJfW3xFaUthiLT0ZGVq0g6n p5rduN94SKYGpdpsYxHhOsNn/eOLJw4IRNfsDYOtGUHQrr5hvxhXDZFg6n1BXBpKtJz0 s8hzlzHe79ymk/jDevdYVK8GxR/Dxxu5hmEcc= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1715084400; x=1715689200; 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=YRLVjkv17D9aBha14p2zSizQpD/IHwVWplpoCtaVJyk=; b=RM0Ogq5+CoTwyGnKgtkwwC91pw6kZ6OKT5yS+qPcQauJnuyAIAnnebCPyxSFMkF/zY Ses8S0GG+8QrIKCgLsgGWVdMV8dX39Ol6limi1piEcBJAQ8TvILhmnGaBgurUPbq4XPp xNOFlFw+fmREOj5lUSMkdqqznykTQ/ldKfAbdzZazD1Cb+U+uL4V5RQeF1lCT7pKSUW3 UQ2OpKmw3gkWJeiVFPyrqHN+Qyvb2bvF6U0ArQdWAHzopYePaDqGKDl91je+W4brZi6d 1KxnTepZfgLrPzfDPpRqyXevHveATjGA5U5V/lFrZ0wh4w1IZFcj2HlXFAcHECvZzNdE 7knA== X-Gm-Message-State: AOJu0Yway3Uqi47uNBUoCClB1oop66DI7kQVhT8X18gukaO9bURKiXOT DbIQkljUcdVEvrLF/AUx+DblPTmUo2AkkdKwq8eF79MdmEOWmbXukXRaB0w1/H4= X-Google-Smtp-Source: AGHT+IEwdWF+ybwuXBQaBxCgzcQ7qQ0nOFVlTuEbMZ5zt0GyuDSonTxlr0DQrl2WmENPxRrGy9dfkA== X-Received: by 2002:a05:620a:2490:b0:78d:5d86:ee3a with SMTP id i16-20020a05620a249000b0078d5d86ee3amr4862746qkn.27.1715084400641; Tue, 07 May 2024 05:20:00 -0700 (PDT) Message-ID: Date: Tue, 7 May 2024 13:19:58 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/cpu-policy: Fix migration from Ice Lake to Cascade Lake To: =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= Cc: Xen-devel , Jan Beulich References: <20240507112957.1701824-1-andrew.cooper3@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 07/05/2024 12:50 pm, Roger Pau Monné wrote: > On Tue, May 07, 2024 at 12:29:57PM +0100, Andrew Cooper wrote: >> Ever since Xen 4.14, there has been a latent bug with migration. >> >> While some toolstacks can level the features properly, they don't shink >> feat.max_subleaf when all features have been dropped. This is because >> we *still* have not completed the toolstack side work for full CPU Policy >> objects. >> >> As a consequence, even when properly feature levelled, VMs can't migrate >> "backwards" across hardware which reduces feat.max_subleaf. One such example >> is Ice Lake (max_subleaf=2 for INTEL_PSFD) to Cascade Lake (max_subleaf=0). >> >> Extend the host policy's feat.max_subleaf to the hightest number Xen knows >> about, similarly to how we extend extd.max_leaf for LFENCE_DISPATCH. This >> will allow VMs with a higher feat.max_subleaf than strictly necessary to >> migrate in. > Seeing what we do for max_extd_leaf, shouldn't we switch to doing what > you propose for feat.max_subleaf to max_extd_leaf also? > > To allow migration between hosts that have 0x80000021.eax and hosts > that don't have such extended leaf. > > cpu_has_lfence_dispatch kind of does that, but if lfence cannot be > made serializing then the max extended leaf is not expanded. And we > should also likely account for more feature leafs possibly appearing > after 0x80000021? On second thoughts, this adjustment ought to be in the max policies only. It's slightly different to LFENCE_DISPATCH, in that we don't actually have any set bits in those leaves. I'll do a different patch. ~Andrew