From patchwork Mon Dec 27 00:32:16 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 529284 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DA634C433EF for ; Mon, 27 Dec 2021 00:32:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234868AbhL0AcT (ORCPT ); Sun, 26 Dec 2021 19:32:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36684 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234866AbhL0AcT (ORCPT ); Sun, 26 Dec 2021 19:32:19 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E9891C06173E; Sun, 26 Dec 2021 16:32:18 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 58BD360F22; Mon, 27 Dec 2021 00:32:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2CDFDC36AE9; Mon, 27 Dec 2021 00:32:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1640565137; bh=iFBH0BixziNnSUfuRfIISjxLeqicavtq7qycaaPTkeY=; h=Date:From:To:Subject:From; b=CCav32kvLma6jur8lahH7b4HSRGUoUqYoQ/lndlSGS3MIWVA/aJIwFkT/mIWU9vVp nnp73q93eXjXxln8I3a3tahzJbrEp29b8hG0J7JXglUP9Wi3BMzWKerHQvZ0RJPCU9 RzmneoQ8z0gDOHC1btfZLZeUvm0RDtQE2sMyC2Nk= Date: Sun, 26 Dec 2021 16:32:16 -0800 From: akpm@linux-foundation.org To: mm-commits@vger.kernel.org, vbabka@suse.cz, stable@vger.kernel.org, robin.murphy@arm.com, rientjes@google.com, penberg@kernel.org, m.szyprowski@samsung.com, john.p.donnelly@oracle.com, iamjoonsoo.kim@lge.com, hch@lst.de, david@redhat.com, David.Laight@ACULAB.COM, cl@linux.com, bp@alien8.de, 42.hyeyoo@gmail.com, bhe@redhat.com Subject: + mm_zone-add-function-to-check-if-managed-dma-zone-exists.patch added to -mm tree Message-ID: <20211227003216.ylCl9%akpm@linux-foundation.org> User-Agent: s-nail v14.9.10 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: mm_zone: add function to check if managed dma zone exists has been added to the -mm tree. Its filename is mm_zone-add-function-to-check-if-managed-dma-zone-exists.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm_zone-add-function-to-check-if-managed-dma-zone-exists.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm_zone-add-function-to-check-if-managed-dma-zone-exists.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Baoquan He Subject: mm_zone: add function to check if managed dma zone exists Patch series "Handle warning of allocation failure on DMA zone w/o managed pages", v4. **Problem observed: On x86_64, when crash is triggered and entering into kdump kernel, page allocation failure can always be seen. --------------------------------- DMA: preallocated 128 KiB GFP_KERNEL pool for atomic allocations swapper/0: page allocation failure: order:5, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0 CPU: 0 PID: 1 Comm: swapper/0 Call Trace: dump_stack+0x7f/0xa1 warn_alloc.cold+0x72/0xd6 ...... __alloc_pages+0x24d/0x2c0 ...... dma_atomic_pool_init+0xdb/0x176 do_one_initcall+0x67/0x320 ? rcu_read_lock_sched_held+0x3f/0x80 kernel_init_freeable+0x290/0x2dc ? rest_init+0x24f/0x24f kernel_init+0xa/0x111 ret_from_fork+0x22/0x30 Mem-Info: ------------------------------------ ***Root cause: In the current kernel, it assumes that DMA zone must have managed pages and try to request pages if CONFIG_ZONE_DMA is enabled. While this is not always true. E.g in kdump kernel of x86_64, only low 1M is presented and locked down at very early stage of boot, so that this low 1M won't be added into buddy allocator to become managed pages of DMA zone. This exception will always cause page allocation failure if page is requested from DMA zone. ***Investigation: This failure happens since below commit merged into linus's tree. 1a6a9044b967 x86/setup: Remove CONFIG_X86_RESERVE_LOW and reservelow= options 23721c8e92f7 x86/crash: Remove crash_reserve_low_1M() f1d4d47c5851 x86/setup: Always reserve the first 1M of RAM 7c321eb2b843 x86/kdump: Remove the backup region handling 6f599d84231f x86/kdump: Always reserve the low 1M when the crashkernel option is specified Before them, on x86_64, the low 640K area will be reused by kdump kernel. So in kdump kernel, the content of low 640K area is copied into a backup region for dumping before jumping into kdump. Then except of those firmware reserved region in [0, 640K], the left area will be added into buddy allocator to become available managed pages of DMA zone. However, after above commits applied, in kdump kernel of x86_64, the low 1M is reserved by memblock, but not released to buddy allocator. So any later page allocation requested from DMA zone will fail. At the beginning, if crashkernel is reserved, the low 1M need be locked down because AMD SME encrypts memory making the old backup region mechanims impossible when switching into kdump kernel. Later, it was also observed that there are BIOSes corrupting memory under 1M. To solve this, in commit f1d4d47c5851, the entire region of low 1M is always reserved after the real mode trampoline is allocated. Besides, recently, Intel engineer mentioned their TDX (Trusted domain extensions) which is under development in kernel also needs to lock down the low 1M. So we can't simply revert above commits to fix the page allocation failure from DMA zone as someone suggested. ***Solution: Currently, only DMA atomic pool and dma-kmalloc will initialize and request page allocation with GFP_DMA during bootup. So only initializ DMA atomic pool when DMA zone has available managed pages, otherwise just skip the initialization. For dma-kmalloc(), for the time being, let's mute the warning of allocation failure if requesting pages from DMA zone while no manged pages. Meanwhile, change code to use dma_alloc_xx/dma_map_xx API to replace kmalloc(GFP_DMA), or do not use GFP_DMA when calling kmalloc() if not necessary. Christoph is posting patches to fix those under drivers/scsi/. Finally, we can remove the need of dma-kmalloc() as people suggested. This patch (of 3): In some places of the current kernel, it assumes that dma zone must have managed pages if CONFIG_ZONE_DMA is enabled. While this is not always true. E.g in kdump kernel of x86_64, only low 1M is presented and locked down at very early stage of boot, so that there's no managed pages at all in DMA zone. This exception will always cause page allocation failure if page is requested from DMA zone. Here add function has_managed_dma() and the relevant helper functions to check if there's DMA zone with managed pages. It will be used in later patches. Link: https://lkml.kernel.org/r/20211223094435.248523-1-bhe@redhat.com Link: https://lkml.kernel.org/r/20211223094435.248523-2-bhe@redhat.com Fixes: 6f599d84231f ("x86/kdump: Always reserve the low 1M when the crashkernel option is specified") Signed-off-by: Baoquan He Reviewed-by: David Hildenbrand Acked-by: John Donnelly Cc: Christoph Hellwig Cc: Christoph Lameter Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Vlastimil Babka Cc: David Laight Cc: Borislav Petkov Cc: Marek Szyprowski Cc: Robin Murphy Cc: Signed-off-by: Andrew Morton --- include/linux/mmzone.h | 9 +++++++++ mm/page_alloc.c | 15 +++++++++++++++ 2 files changed, 24 insertions(+) --- a/include/linux/mmzone.h~mm_zone-add-function-to-check-if-managed-dma-zone-exists +++ a/include/linux/mmzone.h @@ -1046,6 +1046,15 @@ static inline int is_highmem_idx(enum zo #endif } +#ifdef CONFIG_ZONE_DMA +bool has_managed_dma(void); +#else +static inline bool has_managed_dma(void) +{ + return false; +} +#endif + /** * is_highmem - helper function to quickly check if a struct zone is a * highmem zone or not. This is an attempt to keep references --- a/mm/page_alloc.c~mm_zone-add-function-to-check-if-managed-dma-zone-exists +++ a/mm/page_alloc.c @@ -9510,3 +9510,18 @@ bool take_page_off_buddy(struct page *pa return ret; } #endif + +#ifdef CONFIG_ZONE_DMA +bool has_managed_dma(void) +{ + struct pglist_data *pgdat; + + for_each_online_pgdat(pgdat) { + struct zone *zone = &pgdat->node_zones[ZONE_DMA]; + + if (managed_zone(zone)) + return true; + } + return false; +} +#endif /* CONFIG_ZONE_DMA */