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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 DA2A8CA0FF7 for ; Wed, 27 Aug 2025 22:08:22 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7BBA610E8F1; Wed, 27 Aug 2025 22:08:22 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.b="ISyyHl2d"; dkim-atps=neutral Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id E9D3610E8F1 for ; Wed, 27 Aug 2025 22:08:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1756332500; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oNaSehEob45J6rBCmQiuv1tai/IG2I8b55z4DkHJozQ=; b=ISyyHl2dzBLRL0R6zkiMra1zmYPZoXEtyKZSb0TgsgVdgRKJPghW95RftPUSiSHEXWkeKt utW/702cfbjCtbMjJTHXGO8HE8WXCkfRiVapH9Bvstie3HG5ndwGPfXLDgPohcJgAVhfx/ wj4MdQdp9t0Z/+Zpw+l/42lZwrkd9Ok= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-376-aT4Dz_AHNuy0h_90DuEaig-1; Wed, 27 Aug 2025 18:08:13 -0400 X-MC-Unique: aT4Dz_AHNuy0h_90DuEaig-1 X-Mimecast-MFC-AGG-ID: aT4Dz_AHNuy0h_90DuEaig_1756332487 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2D1AD1800296; Wed, 27 Aug 2025 22:08:07 +0000 (UTC) Received: from t14s.redhat.com (unknown [10.22.80.195]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 478603001453; Wed, 27 Aug 2025 22:07:50 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: David Hildenbrand , Alexandru Elisei , 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: [PATCH v1 21/36] mm/cma: refuse handing out non-contiguous page ranges Date: Thu, 28 Aug 2025 00:01:25 +0200 Message-ID: <20250827220141.262669-22-david@redhat.com> In-Reply-To: <20250827220141.262669-1-david@redhat.com> References: <20250827220141.262669-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Let's disallow handing out PFN ranges with non-contiguous pages, so we can remove the nth-page usage in __cma_alloc(), and so any callers don't have to worry about that either when wanting to blindly iterate pages. This is really only a problem in configs with SPARSEMEM but without SPARSEMEM_VMEMMAP, and only when we would cross memory sections in some cases. Will this cause harm? Probably not, because it's mostly 32bit that does not support SPARSEMEM_VMEMMAP. If this ever becomes a problem we could look into allocating the memmap for the memory sections spanned by a single CMA region in one go from memblock. Reviewed-by: Alexandru Elisei Signed-off-by: David Hildenbrand --- include/linux/mm.h | 6 ++++++ mm/cma.c | 39 ++++++++++++++++++++++++--------------- mm/util.c | 33 +++++++++++++++++++++++++++++++++ 3 files changed, 63 insertions(+), 15 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index f6880e3225c5c..2ca1eb2db63ec 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -209,9 +209,15 @@ extern unsigned long sysctl_user_reserve_kbytes; extern unsigned long sysctl_admin_reserve_kbytes; #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP) +bool page_range_contiguous(const struct page *page, unsigned long nr_pages); #define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n)) #else #define nth_page(page,n) ((page) + (n)) +static inline bool page_range_contiguous(const struct page *page, + unsigned long nr_pages) +{ + return true; +} #endif /* to align the pointer to the (next) page boundary */ diff --git a/mm/cma.c b/mm/cma.c index e56ec64d0567e..813e6dc7b0954 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -780,10 +780,8 @@ static int cma_range_alloc(struct cma *cma, struct cma_memrange *cmr, unsigned long count, unsigned int align, struct page **pagep, gfp_t gfp) { - unsigned long mask, offset; - unsigned long pfn = -1; - unsigned long start = 0; unsigned long bitmap_maxno, bitmap_no, bitmap_count; + unsigned long start, pfn, mask, offset; int ret = -EBUSY; struct page *page = NULL; @@ -795,7 +793,7 @@ static int cma_range_alloc(struct cma *cma, struct cma_memrange *cmr, if (bitmap_count > bitmap_maxno) goto out; - for (;;) { + for (start = 0; ; start = bitmap_no + mask + 1) { spin_lock_irq(&cma->lock); /* * If the request is larger than the available number @@ -812,6 +810,22 @@ static int cma_range_alloc(struct cma *cma, struct cma_memrange *cmr, spin_unlock_irq(&cma->lock); break; } + + pfn = cmr->base_pfn + (bitmap_no << cma->order_per_bit); + page = pfn_to_page(pfn); + + /* + * Do not hand out page ranges that are not contiguous, so + * callers can just iterate the pages without having to worry + * about these corner cases. + */ + if (!page_range_contiguous(page, count)) { + spin_unlock_irq(&cma->lock); + pr_warn_ratelimited("%s: %s: skipping incompatible area [0x%lx-0x%lx]", + __func__, cma->name, pfn, pfn + count - 1); + continue; + } + bitmap_set(cmr->bitmap, bitmap_no, bitmap_count); cma->available_count -= count; /* @@ -821,29 +835,24 @@ static int cma_range_alloc(struct cma *cma, struct cma_memrange *cmr, */ spin_unlock_irq(&cma->lock); - pfn = cmr->base_pfn + (bitmap_no << cma->order_per_bit); mutex_lock(&cma->alloc_mutex); ret = alloc_contig_range(pfn, pfn + count, ACR_FLAGS_CMA, gfp); mutex_unlock(&cma->alloc_mutex); - if (ret == 0) { - page = pfn_to_page(pfn); + if (!ret) break; - } cma_clear_bitmap(cma, cmr, pfn, count); if (ret != -EBUSY) break; pr_debug("%s(): memory range at pfn 0x%lx %p is busy, retrying\n", - __func__, pfn, pfn_to_page(pfn)); + __func__, pfn, page); - trace_cma_alloc_busy_retry(cma->name, pfn, pfn_to_page(pfn), - count, align); - /* try again with a bit different memory target */ - start = bitmap_no + mask + 1; + trace_cma_alloc_busy_retry(cma->name, pfn, page, count, align); } out: - *pagep = page; + if (!ret) + *pagep = page; return ret; } @@ -882,7 +891,7 @@ static struct page *__cma_alloc(struct cma *cma, unsigned long count, */ if (page) { for (i = 0; i < count; i++) - page_kasan_tag_reset(nth_page(page, i)); + page_kasan_tag_reset(page + i); } if (ret && !(gfp & __GFP_NOWARN)) { diff --git a/mm/util.c b/mm/util.c index d235b74f7aff7..0bf349b19b652 100644 --- a/mm/util.c +++ b/mm/util.c @@ -1280,4 +1280,37 @@ unsigned int folio_pte_batch(struct folio *folio, pte_t *ptep, pte_t pte, { return folio_pte_batch_flags(folio, NULL, ptep, &pte, max_nr, 0); } + +#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP) +/** + * page_range_contiguous - test whether the page range is contiguous + * @page: the start of the page range. + * @nr_pages: the number of pages in the range. + * + * Test whether the page range is contiguous, such that they can be iterated + * naively, corresponding to iterating a contiguous PFN range. + * + * This function should primarily only be used for debug checks, or when + * working with page ranges that are not naturally contiguous (e.g., pages + * within a folio are). + * + * Returns true if contiguous, otherwise false. + */ +bool page_range_contiguous(const struct page *page, unsigned long nr_pages) +{ + const unsigned long start_pfn = page_to_pfn(page); + const unsigned long end_pfn = start_pfn + nr_pages; + unsigned long pfn; + + /* + * The memmap is allocated per memory section. We need to check + * each involved memory section once. + */ + for (pfn = ALIGN(start_pfn, PAGES_PER_SECTION); + pfn < end_pfn; pfn += PAGES_PER_SECTION) + if (unlikely(page + (pfn - start_pfn) != pfn_to_page(pfn))) + return false; + return true; +} +#endif #endif /* CONFIG_MMU */ -- 2.50.1