From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D12FD606A8B6 for ; Thu, 12 Nov 2026 08:49:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=blR2ZZkc Received: by kanga.kvack.org (Postfix) id D3CD06B05B6; Thu, 12 Nov 2026 03:49:56 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D13B66B05D6; Thu, 12 Nov 2026 03:49:56 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C525E6B05D7; Thu, 12 Nov 2026 03:49:56 -0500 (EST) 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 989CF6B05B6 for ; Thu, 12 Nov 2026 03:49:56 -0500 (EST) Received: from smtpin03.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 29C5414050D for ; Thu, 12 Nov 2026 08:49:56 +0000 (UTC) X-FDA: 85425844392.03.4935813 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf04.hostedemail.com (Postfix) with ESMTP id 7059440004 for ; Thu, 12 Nov 2026 08:49:54 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=blR2ZZkc; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf04.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=rppt@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1794473394; b=J1jA9OuehUJhyq2ost2QdyMlR56SuEPHNbo97aF87awJdPKs/1xSu9PKUGg0FRcf79N9FZ ix5XtIabHxdufcxTTKSPhv47TwaLJ9PXtu2fwuFtt4GJPGsqzdlgk3vgsLKoVQ9efAW3Dk 8zxA+h468Pny6CTUgc5Pny73+Yiac6E= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1794473394; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=OGChezwGEAs5VmxdKN/i88B/dah14lbYLutkEhF0lOY=; b=RdcJ/+hPOkkEYGkemwqKLNuemScbe4ggYV1LDNEKJ0f7ZO1tqTI70ULjBwouWZQcuJIkj5 Bq31CMgn2JP14jrZJVQL531k+Rqc1nuHBAyCz8LP0T93BWPkM4rQcaOi2o39ePUfcO/I5H Ap/PA6jhZd/aqmOPiwK01IaOIgEQSfM= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=blR2ZZkc; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf04.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=rppt@kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id AE97D43645; Thu, 12 Nov 2026 08:49:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BA7AE1F00A05; Thu, 12 Nov 2026 08:49:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794473393; bh=OGChezwGEAs5VmxdKN/i88B/dah14lbYLutkEhF0lOY=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=blR2ZZkcc/vDDO96F1pNxo2m29Sm1eEE58wpJKJVkHYo/oXT8bnVVxwZZly5gZt9q WjKhsecawJUo7hwiLqoB1tVNvATaSKrnCQij9ms9i4j046DyigYLVgzKpPVW/Tm32u DFsGgSAhvGZFpD7jZe6hMTEs8q6xFGpoAsvodr12hfkgt1d+rnYLrT4Zo91RMnmygO 0yruuXkzYrHRiuER+joOHfZNGA23QqvNVf/8ozCvJuVQ3b+UfYkf9kKtv/5ozkNjEA SJWrIn3UVe4emvFMOq5MsjJhsAU82JyD7Ikm8arKDsaA71v1lyHUIdzvm0qEtUhFC4 NtcmR0wFZxi0g== Date: Thu, 12 Nov 2026 10:49:46 +0200 From: Mike Rapoport To: Mukesh Pilaniya Cc: Pasha Tatashin , Pratyush Yadav , Alexander Graf , Andrew Morton , Chen Pei , George Guo , Kexin Liu , Sourabh Jain , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 1/3] kho: walk bootmem areas in address order Message-ID: References: <20261104-kho-bootmem-sizing-v2-0-b0d1a834780f@kernel.org> <20261104-kho-bootmem-sizing-v2-1-b0d1a834780f@kernel.org> <990cc079-70ab-4fcf-9974-679aaf07849e@redhat.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <990cc079-70ab-4fcf-9974-679aaf07849e@redhat.com> X-Rspamd-Queue-Id: 7059440004 X-Rspamd-Server: rspam12 X-Stat-Signature: ysmzuaqznrm9oxyju9g7hb4rbfcm5c11 X-Rspam-User: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=unavailable autolearn_force=no version=4.0.1 X-HE-Tag: 1794473394-559673 X-HE-Meta: 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 12JJ5ELG 4o5eLyBfTv9dvF4II0k3HrSVgCtPX1okOFFlNPrVwDLPW14g/efd4skJZu6sfRge5stS/KI0gLTSGQ5HiAL0t2PonddTljGOA+LL9fVKcyybCRtm+Ml4ecPPC6tqLgfNh0FCPCwbkwsetOYV9p1RtpNZMJUclZRK0RcicZmZgChbikcK6uDhKSdj8Ny2TrIILGf9veFLLm5YnrbwCnr3dA5JYgTRawAjiHtDIzmiHD4aVwc0PhHNpTpM9+mTW0wzz0pFZG85d5CcJYh8xI65nZoGzvwOcbMBkcEkgJNhZWy1XhZOSKd+5i1ti1mJRfbsSFL2T1Z50ZnBdovWFzvzxzV8xxekXBmQqYvBxtpHapA4GNyWUHNvzK9b5XWVqBNClPpP4TuogagYD3WH2hAkTY18QTnlAZUvUtMKX5Aa0y52n+R5IqUzNVVeOFEi8NdOYrmTfaI45M6iV12Q= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, Nov 12, 2026 at 12:02:05PM +0530, Mukesh Pilaniya wrote: > Hi Mike, > > On 04/11/26 10:20 pm, Mike Rapoport (Microsoft) wrote: > > kexec_add_buffer() users may depend on the order in which memory holes are > > searched. For instance, arm64 places the kernel bottom-up and then > > requires the DTB to be above the kernel. > > > > kho_walk_bootmem() walks the bootmem areas in the order they were > > reserved, so if the kernel lands in a small area at the top of the memory > > there is no room left for the DTB and kexec fails. For example, on an > > arm64 VM with 2G of RAM and kho_bootmem=8M,64M,64M, the lowmem area is > > reserved first at the top of the memory, the kernel image takes most of > > it and kexec fails with > > > > kexec_file(Image): Could not find any suitable kernel location! > > > > Sort the bootmem areas by address and walk them in ascending order, or in > > descending order for top-down searches, like kexec_walk_resources() does. > > > > Fixes: 3bdecc3c93f9 ("kexec: add KHO support to kexec file loads") > > Signed-off-by: Mike Rapoport (Microsoft) > > --- > > kernel/liveupdate/kexec_handover.c | 57 ++++++++++++++++++++++++++++++-------- > > 1 file changed, 46 insertions(+), 11 deletions(-) > > > > diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c > > index 6f1f55fe31819..2ac5d94f33fd4 100644 > > --- a/kernel/liveupdate/kexec_handover.c > > +++ b/kernel/liveupdate/kexec_handover.c > > @@ -26,6 +26,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > > > @@ -820,6 +821,14 @@ bool kho_bootmem_overlap(phys_addr_t phys, size_t size) > > return false; > > } > > > > +static int __init kho_bootmem_cmp(const void *_a, const void *_b) > > +{ > > + const struct kho_bootmem *a = _a; > > + const struct kho_bootmem *b = _b; > > + > > + return cmp_int(a->addr, b->addr); > > +} > > + > > /** > > * kho_reserve_bootmem - Reserve a contiguous chunk of memory for kexec > > * > > @@ -904,6 +913,9 @@ static void __init kho_reserve_bootmem(void) > > */ > > kho_bootmem_cnt = i; > > > > + sort(kho_bootmem, kho_bootmem_cnt, sizeof(*kho_bootmem), > > + kho_bootmem_cmp, NULL); > This only covers the case where this kernel allocated the areas itself. > On a KHO boot the array comes from the previous kernel. A kernel with > this series that is handed over from one without it therefore keeps > walking the areas in reservation order for every following > kexec_file_load, and the arm64 failure you describe comes back until the > next cold boot and vise versa because the ABI string is still > "kho-v4". If we were able to kexec from a kernel with no reservation ordering, the issue is not there, isn't it? And after a cycle of KHO boots to newer kernels we anyway can get to the point when bootmem is not large enough. > > +static int kho_bootmem_walk_top_down(struct kexec_buf *kbuf, > > + int (*func)(struct resource *, void *)) > > { > > int ret = 0; > > - int i; > > > > - for (i = 0; i < kho_bootmem_cnt; i++) { > > - struct resource res = { > > - .start = kho_bootmem[i].addr, > > - .end = kho_bootmem[i].addr + kho_bootmem[i].size - 1, > > - }; > > + for (int i = kho_bootmem_cnt - 1; i >= 0; i--) { > > kho_bootmem_cnt is unsigned, but the reverse loops in > kho_reserve_bootmem() and kho_bootmem_walk_top_down() start an int > counter at kho_bootmem_cnt - 1, which for a zero count is UINT_MAX > converted to int. That conversion is implementation-defined; with the > current compilers it yields -1 and the loop body is skipped. We never get here with kho_bootmem_cnt == 0. > How about using this one. > for (unsigned int i = kho_bootmem_cnt; i-- > 0;) > > Reviewed-by: Mukesh Pilaniya Thanks! > -- > Regards, > Mukesh Pilaniya > -- Sincerely yours, Mike.