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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7EF48ECD98A for ; Thu, 5 Feb 2026 17:29:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7348F6B0089; Thu, 5 Feb 2026 12:29:17 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6E1F06B008A; Thu, 5 Feb 2026 12:29:17 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 58F846B0092; Thu, 5 Feb 2026 12:29:17 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 453C36B0089 for ; Thu, 5 Feb 2026 12:29:17 -0500 (EST) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 004DC160653 for ; Thu, 5 Feb 2026 17:29:16 +0000 (UTC) X-FDA: 84411089154.08.6E89667 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf09.hostedemail.com (Postfix) with ESMTP id 390B2140009 for ; Thu, 5 Feb 2026 17:29:15 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=gxWACkGJ; spf=pass (imf09.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1770312555; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=XzZvidWsus7OtK4lFAmO2lKtoJo1W0yiwW6FWu0uFdY=; b=EUwn35gy6+SYLHt7EaqjbFspkh8JEQSx1RBbq+MV58/jEBoLr1sX7nFLrqAmgHYxTouXzJ 42N62MtlqeyURhfyi1Hyq3gS0Tj2dOPpdjHugxz8/dvCGyZ2SJ+EDq1PlkYao/Ty/PZ2iH 6qc1o+wMPGa0vbBmH78+SaWSAJXQdgo= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=gxWACkGJ; spf=pass (imf09.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1770312555; a=rsa-sha256; cv=none; b=ipPaSUU2V2eUbLWRuThDAHUjJmA6fmfxuEAND+KmWkwgkaHYugoiarH4graw7liUe7yGLb 6TJlxcx0oAygqiFVcRaUN0NSJlCRaaRfkCQfOS6HS8qxB1mRDZGuWie2c9iIenX8C6Fvjv TCxkoCrzQeUhkTDLr/sBRQHzmukEarI= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 8DF0660010; Thu, 5 Feb 2026 17:29:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 898D0C19421; Thu, 5 Feb 2026 17:29:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770312554; bh=0h6aXl3odpNK6UOPrFIUbCWh+xiPmUDlXpbqQDhrshE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=gxWACkGJV7DkZqdSO+Yr0POPlWnhgxybc9tAg6dxFEhlVjQlQtKtTIljdTT0hzq1+ h8KjD/VSTs3PLX2jFPkpp7je/j4DVJ107VFASmwRWRQu9HifVKwjMEwB89Ys0I7AXN c4e7RWEYNhNIONgGGL8jGEk5AyQRP93D3O+W7h6musIYXU+WV2OZEHgFg2TUlEH7hU Zv5T98JKbPMN2oOy8HhGH/F4Tc46+No1HTfVOyElgCAKIQP2E2ietHeFJ6qYJT7nvF xt16dahFoksybify+15Y+KDDncnYDnt16EK3DBG4Nz74Q1TpRdXr60fH5nZ4fBsbxd 8uR5SZdgstrkw== Message-ID: Date: Thu, 5 Feb 2026 18:29:08 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 1/2] mm/memory_hotplug: Add support to accept memory during hot-add To: Kiryl Shutsemau Cc: "Pratik R. Sampat" , linux-mm@kvack.org, linux-coco@lists.linux.dev, x86@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, ardb@kernel.org, akpm@linux-foundation.org, osalvador@suse.de, thomas.lendacky@amd.com, michael.roth@amd.com References: <20260203174946.1198053-1-prsampat@amd.com> <20260203174946.1198053-2-prsampat@amd.com> <70be936e-e49d-4485-8d1e-416fdf8f40a4@amd.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: hzzwcq7w5f17akm7pp4hpxt91zn1qhuc X-Rspamd-Queue-Id: 390B2140009 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1770312555-450946 X-HE-Meta: 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 DBQrpe1u Y8FLdhxXNAmlJcaahiQWnmBtqUbzT3P2WLgEwg62kbYRyYcsUOt4E09OtL23Sf5wslgaRPAT4dnsXR70cx+j0LBoZj+oVAscwKjkNkyetHZmeolv2m+lTFqCDb21R+FOUUbOOsRoKNdIB6qczNb4qB1z6utYbLw3RuxC89Xkas7r1eNNGzeFo5mSlxR2RWa3g7RjRKNDVMEHbpvJZTX8tecpuPi2F3271ELetdnD63JDfvW84HT4cSMGL1Rmm+ngqmnPvQY2KbKLV0BiDlX1YbIPvwFXlgCfnvjFt0m7qtSS3RiHIwnyluHLZXA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/5/26 17:08, Kiryl Shutsemau wrote: > On Thu, Feb 05, 2026 at 04:48:13PM +0100, David Hildenbrand (Arm) wrote: >> On 2/5/26 11:48, Kiryl Shutsemau wrote: >>> >>> You are calling arch_accept_memory() on every memory allocation if the >>> memory is not represented in the bitmap. Hard NAK. >> >> In which scenarios would we not have memory represented in the bitmap? >> Guests with <4 GiB? (how does kexec work?) Anything else? > > We create the bitmap that covers all unaccepted memory. Good! :) > > What memory is unaccepted is up to BIOS. Current implementation of edk2 > accepts the memory in the first 4G range of physical address space. It > means we won't have bitmap for this range (unaccepted->phys_base >= 4G). Ah, okay, this comes from the BIOS. > > If the whole VM is smaller than 4G we won't have the bitmap at all. > > We can allocate bitmap for all possible memory. Maybe upto max_possible_pfn? > But we might not know the value in EFI stub. It costs 4k per 64GiB of > physical address space. That's what I would do. 4k per 64GiB sounds reasonable. > > Ideally, we want to know on boot: > > - what memory ranges are unaccepted - we have it; > - what memory range can be removed or added after boot - we don't have it The SRAT describes memory ranges where we can see hotplug memory. Is that too late? We calculate max_possible_pfn based on that. (don't ask me about special CXL windows and how they are advertised :) ) -- Cheers, David