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 2624DC982C5 for ; Wed, 16 Sep 2026 14:51:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1B7966B0088; Wed, 16 Sep 2026 10:51:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 168B06B0095; Wed, 16 Sep 2026 10:51:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 02F986B0099; Wed, 16 Sep 2026 10:51:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id CA9506B0088 for ; Wed, 16 Sep 2026 10:51:52 -0400 (EDT) Received: from smtpin13.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 61B3AA5B4D for ; Wed, 16 Sep 2026 14:51:52 +0000 (UTC) X-FDA: 85219914864.13.8772E83 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf28.hostedemail.com (Postfix) with ESMTP id 9101AC0007 for ; Wed, 16 Sep 2026 14:51:50 +0000 (UTC) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=DJmX77mg; spf=pass (imf28.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789570310; b=a1yRwWrDF9KctEB8G0M5zH65hBu5NTdJ23VekFAGZWaY8LZKwLqE7td6Gt5DiP1losux4M 8hWgPCK0k8a+7ijRUmR2x3R8QmZSzaC58QFG8omwuRgwmwyLfZmyhxE5Yg/q5aFUBj2wNk NOTLkKmkmU7Of4ISKVQ1eLBYedGI4eA= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=DJmX77mg; spf=pass (imf28.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 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=1789570310; 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=s9b/9Hwh5vUHfr3h3yI1jv7U58Y0A9HgrBxLkX3sPvA=; b=4f2tpXlJQPWONxjrZ9XhS91vhQUvxkjRLuVdZVLq+XgqA4kSFw8qF1rBVk4zez5rnfJw+1 wmS+4P2E9UvSndArinuvfkV1kTIOaR8bh2HjZnUZlgbtaWuzlnUukEBFv12jeBPbkt8/bZ FYHZ4SN0Ffz+Dh58uiLZVu2HcOklT1s= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id B742540367; Wed, 16 Sep 2026 14:51:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1141A1F00898; Wed, 16 Sep 2026 14:51:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789570309; bh=s9b/9Hwh5vUHfr3h3yI1jv7U58Y0A9HgrBxLkX3sPvA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=DJmX77mgdbs6Q8GAXeo0braYp2Bik3mxuTOg0XuCWiVphbHAn0kd2P/Gl+uG+6WHV Nj7WIlnKvMiHz2i5VCCjR0CKoRaRenUKdVTz4v8buhxLZCDYs7IWCtsnkMkJY5qML5 abKuZvlhV5VK8XsDgdsDHh2VJyTT/NPOcB+cu8l4dl4wTx3cP9yEipHHWuu3Sstsgs w2BFWBemQKvOXthe2X/HXPSb4U4WjkI1WB1QXgotSE6z7uqoNYpuGUaxbqDGsHaugi qFBqz/j/wpD9Z4FAxE0BIjGvJbIomrHP3AiW+U8sR6kKKimRJUHOhADx5jFJ6fVP0H hUGLHYw9SMtJQ== Message-ID: Date: Wed, 16 Sep 2026 16:51:40 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 7/9] drivers/base/memory: count inherited poisoned frames into the block To: Breno Leitao Cc: Ard Biesheuvel , Ilias Apalodimas , Miaohe Lin , Naoya Horiguchi , Andrew Morton , kas@kernel.org, kexec@lists.infradead.org, Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Brendan Jackman , Johannes Weiner , Zi Yan , Oscar Salvador , Greg Kroah-Hartman , "Rafael J. Wysocki" , Danilo Krummrich , hannes@cmpxchg.or, shakeel.butt@linux.dev, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, rmikey@meta.com, riel@surriel.com, harry@kernel.org, linux-cxl@vger.kernel.org, driver-core@lists.linux.dev, kernel-team@meta.com References: <20260915-hwpoison-kho-v5-0-3bc7a57bd503@debian.org> <20260915-hwpoison-kho-v5-7-3bc7a57bd503@debian.org> 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 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 9101AC0007 X-Rspam-User: X-Stat-Signature: sxqmtpc9sbkxd655onj9maceejmx4ysa X-HE-Tag: 1789570310-341643 X-HE-Meta: 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 lVe2juL1 qonWLBdxPgtrqQnS6Aw2ypyZ5lQakH95OtIfQfDYfGeQzLd9pZ5h0UyyRfW4gLCTz0VinH3XRi6I6q7BBZZWJ0OG+dv3uaOhvQ5WmM5Jx7meEuX62NhS86HGMMJFfli8OKpnY1OUiT3yt3pjafrA+oZQVuZ09h7His38p8WahWzNmnNVQkjO4R/GUMi0j3wWaXTjLXxV6+HRJK434lKHqCVH5bZl2ouRvxeSgEZ25G4I6pDTI44Q3p7YN+Qs8uCZwMF+ZnMoo6NNlnDE3kZCeaiomy5FzQHDLV4IwFRe2KEX9k7gYwYKHaWfjocQPCg3foFUmKMWux5FcMu0ZE253WLXi6bJOiGS3jgI7hkQKHr0Ab84= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/16/26 11:35, Breno Leitao wrote: > Hello David, > > First of all, thanks for your time looking at this patchset. > > On Wed, Sep 16, 2026 at 08:48:56AM +0200, David Hildenbrand (Arm) wrote: >> On 9/15/26 14:53, Breno Leitao wrote: >>> +static void memblk_nr_poison_init(struct memory_block *mem) >>> +{ >>> + unsigned long pfn = section_nr_to_pfn(mem->start_section_nr); >>> + unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block; >>> + unsigned long i, nr_poison = 0; >>> + >>> + /* A hotplugged block is created before its pages are online. */ >>> + if (mem->state != MEM_ONLINE) >>> + return; >>> + >>> + if (!range_contains_poisoned_memory(PFN_PHYS(pfn), >>> + nr_pages << PAGE_SHIFT)) >>> + return; >>> + >>> + for (i = 0; i < nr_pages; i++) { >>> + struct page *page = pfn_to_online_page(pfn + i); >>> + >>> + if (page && PageHWPoison(page)) >>> + nr_poison++; >>> + } >> >> That just slows down boot unnecessarily on 99.9999999999999999999% of all >> systems out there. > > hmmm, I am not sure I see it that way. > > The loop only runs for a block the bitmap marks. On a machine with nothing > recorded the bitmap is all zeros, the range_contains_poisoned_memory() check > right above it returns false, and the loop never executes. > > What every boot does pay is that check, once per block. The stub installs > the table whether or not anything was ever recorded in it, so this is not a > NULL test: it is two 64-bit divisions by the unit size plus a > find_next_bit() over the single word a 128M block covers at one bit per 2M. > > The real cost (that "for loop above"), comes when you kexec (not on cold > boot -- given the bitmap is empty), and you are trying to init > a memory block that has poisoned pages into it. Which seems the right > trade-off, no? > > That said, can we do better? Yes. The silly win is to let the table say > whether anything was ever recorded in it, something like a > linux_efi_poisoned_memory->empty that the first recorded frame clears, > and return on that before the bitmap is reached at all. > > Is this what you are looking for, or something more drastic? Ah, that magical "range_contains_poisoned_memory" does a bitmap scan? I'm sorry, but that is absolutely confusing. There is no way someone will figure out that range_contains_poisoned_memory() queries some efi specific bitmap that won't even be able to represent any memory outside of it's range. I don't really have time to give a better solution, but starting with the naming, range_contains_poisoned_memory() is just absolutely misleading. -- Cheers, David