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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 D7779CA0FE9 for ; Tue, 26 Aug 2025 13:06:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=69etOkI2BEM0MfKuXmsCuTRwt0KN4+vJ8H43fwabGSk=; b=oWieLHzw3opnbz RfXiPCAPy+4IkMvDFA7djfZHCkc+oOn8OY0xW5s26kEmZkKfQDbOyvZFXs5n9FT61cqYNW1V9wYM7 BZsMzRvQ/+0CItmR9+kTZpnL2m4Xv6OFx3dzD2kL/VthnfX1reWbqd0qYJ6E1dyq95FtT7zbLs2cs S9EEBKJ70roFrEEyFoend1RMdY2AXnnWQamrFTwLa+3n+lDS9mVthPxZ1RUKlorjkWaqnjc5b+AhE EgOoN/UZgEW9qim8REQXKjwZH0kSU1sTVQ7lbhLrULVNPTuowIJ6B4VT9O0Q8JFtLmVpvKOkLkBpZ NvMv2HWKdnUvb5iUb7fQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uqtNQ-0000000C29J-1T3D; Tue, 26 Aug 2025 13:06:16 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uqtKh-0000000C1jj-1QJL; Tue, 26 Aug 2025 13:03:28 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 025E02C23; Tue, 26 Aug 2025 06:03:18 -0700 (PDT) Received: from raptor (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A5B423F63F; Tue, 26 Aug 2025 06:03:19 -0700 (PDT) Date: Tue, 26 Aug 2025 14:03:16 +0100 From: Alexandru Elisei To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, Alexander Potapenko , Andrew Morton , Brendan Jackman , Christoph Lameter , Dennis Zhou , Dmitry Vyukov , dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, iommu@lists.linux.dev, io-uring@vger.kernel.org, Jason Gunthorpe , Jens Axboe , Johannes Weiner , John Hubbard , kasan-dev@googlegroups.com, kvm@vger.kernel.org, "Liam R. Howlett" , Linus Torvalds , linux-arm-kernel@axis.com, linux-arm-kernel@lists.infradead.org, linux-crypto@vger.kernel.org, linux-ide@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mips@vger.kernel.org, linux-mmc@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, Lorenzo Stoakes , Marco Elver , Marek Szyprowski , Michal Hocko , Mike Rapoport , Muchun Song , netdev@vger.kernel.org, Oscar Salvador , Peter Xu , Robin Murphy , Suren Baghdasaryan , Tejun Heo , virtualization@lists.linux.dev, Vlastimil Babka , wireguard@lists.zx2c4.com, x86@kernel.org, Zi Yan Subject: Re: [PATCH RFC 21/35] mm/cma: refuse handing out non-contiguous page ranges Message-ID: References: <20250821200701.1329277-1-david@redhat.com> <20250821200701.1329277-22-david@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250826_060327_421136_4941519B X-CRM114-Status: GOOD ( 18.26 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org Hi David, On Tue, Aug 26, 2025 at 01:04:33PM +0200, David Hildenbrand wrote: .. > > Just so I can better understand the problem being fixed, I guess you can have > > two consecutive pfns with non-consecutive associated struct page if you have two > > adjacent memory sections spanning the same physical memory region, is that > > correct? > > Exactly. Essentially on SPARSEMEM without SPARSEMEM_VMEMMAP it is not > guaranteed that > > pfn_to_page(pfn + 1) == pfn_to_page(pfn) + 1 > > when we cross memory section boundaries. > > It can be the case for early boot memory if we allocated consecutive areas > from memblock when allocating the memmap (struct pages) per memory section, > but it's not guaranteed. Thank you for the explanation, but I'm a bit confused by the last paragraph. I think what you're saying is that we can also have the reverse problem, where consecutive struct page * represent non-consecutive pfns, because memmap allocations happened to return consecutive virtual addresses, is that right? If that's correct, I don't think that's the case for CMA, which deals out contiguous physical memory. Or were you just trying to explain the other side of the problem, and I'm just overthinking it? Thanks, Alex _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv