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From: Mike Rapoport <rppt@kernel.org>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, Huacai Chen <chenhuacai@kernel.org>,
	WANG Xuerui <kernel@xen0n.name>,
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	Zi Yan <ziy@nvidia.com>
Subject: Re: [PATCH RFC 01/35] mm: stop making SPARSEMEM_VMEMMAP user-selectable
Date: Fri, 22 Aug 2025 18:09:03 +0300	[thread overview]
Message-ID: <aKiID8i6dYrlVi5T@kernel.org> (raw)
In-Reply-To: <20250821200701.1329277-2-david@redhat.com>

On Thu, Aug 21, 2025 at 10:06:27PM +0200, David Hildenbrand wrote:
> In an ideal world, we wouldn't have to deal with SPARSEMEM without
> SPARSEMEM_VMEMMAP, but in particular for 32bit SPARSEMEM_VMEMMAP is
> considered too costly and consequently not supported.
> 
> However, if an architecture does support SPARSEMEM with
> SPARSEMEM_VMEMMAP, let's forbid the user to disable VMEMMAP: just
> like we already do for arm64, s390 and x86.
> 
> So if SPARSEMEM_VMEMMAP is supported, don't allow to use SPARSEMEM without
> SPARSEMEM_VMEMMAP.
> 
> This implies that the option to not use SPARSEMEM_VMEMMAP will now be
> gone for loongarch, powerpc, riscv and sparc. All architectures only
> enable SPARSEMEM_VMEMMAP with 64bit support, so there should not really
> be a big downside to using the VMEMMAP (quite the contrary).
> 
> This is a preparation for not supporting
> 
> (1) folio sizes that exceed a single memory section
> (2) CMA allocations of non-contiguous page ranges
> 
> in SPARSEMEM without SPARSEMEM_VMEMMAP configs, whereby we
> want to limit possible impact as much as possible (e.g., gigantic hugetlb
> page allocations suddenly fails).
> 
> Cc: Huacai Chen <chenhuacai@kernel.org>
> Cc: WANG Xuerui <kernel@xen0n.name>
> Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
> Cc: Paul Walmsley <paul.walmsley@sifive.com>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> Cc: Albert Ou <aou@eecs.berkeley.edu>
> Cc: Alexandre Ghiti <alex@ghiti.fr>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Andreas Larsson <andreas@gaisler.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
>  mm/Kconfig | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 4108bcd967848..330d0e698ef96 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -439,9 +439,8 @@ config SPARSEMEM_VMEMMAP_ENABLE
>  	bool
>  
>  config SPARSEMEM_VMEMMAP
> -	bool "Sparse Memory virtual memmap"
> +	def_bool y
>  	depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
> -	default y
>  	help
>  	  SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
>  	  pfn_to_page and page_to_pfn operations.  This is the most
> -- 
> 2.50.1
> 

-- 
Sincerely yours,
Mike.

  parent reply	other threads:[~2025-08-22 15:09 UTC|newest]

Thread overview: 90+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-08-21 20:06 [PATCH RFC 00/35] mm: remove nth_page() David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 01/35] mm: stop making SPARSEMEM_VMEMMAP user-selectable David Hildenbrand
2025-08-21 20:20   ` Zi Yan
2025-08-22 15:09   ` Mike Rapoport [this message]
2025-08-22 17:02   ` SeongJae Park
2025-08-21 20:06 ` [PATCH RFC 02/35] arm64: Kconfig: drop superfluous "select SPARSEMEM_VMEMMAP" David Hildenbrand
2025-08-22 15:10   ` Mike Rapoport
2025-08-21 20:06 ` [PATCH RFC 03/35] s390/Kconfig: " David Hildenbrand
2025-08-22 15:11   ` Mike Rapoport
2025-08-21 20:06 ` [PATCH RFC 04/35] x86/Kconfig: " David Hildenbrand
2025-08-22 15:11   ` Mike Rapoport
2025-08-21 20:06 ` [PATCH RFC 05/35] wireguard: selftests: remove CONFIG_SPARSEMEM_VMEMMAP=y from qemu kernel config David Hildenbrand
2025-08-22 15:13   ` Mike Rapoport
2025-08-21 20:06 ` [PATCH RFC 06/35] mm/page_alloc: reject unreasonable folio/compound page sizes in alloc_contig_range_noprof() David Hildenbrand
2025-08-21 20:23   ` Zi Yan
2025-08-22 17:07   ` SeongJae Park
2025-08-21 20:06 ` [PATCH RFC 07/35] mm/memremap: reject unreasonable folio/compound page sizes in memremap_pages() David Hildenbrand
2025-08-22 17:09   ` SeongJae Park
2025-08-21 20:06 ` [PATCH RFC 08/35] mm/hugetlb: check for unreasonable folio sizes when registering hstate David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 09/35] mm/mm_init: make memmap_init_compound() look more like prep_compound_page() David Hildenbrand
2025-08-22 15:27   ` Mike Rapoport
2025-08-22 18:09     ` David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 10/35] mm/hugetlb: cleanup hugetlb_folio_init_tail_vmemmap() David Hildenbrand
2025-08-22  4:09   ` Mika Penttilä
2025-08-22  6:24     ` David Hildenbrand
2025-08-23  8:59       ` Mike Rapoport
2025-08-25 12:48         ` David Hildenbrand
2025-08-25 14:32           ` Mike Rapoport
2025-08-25 14:38             ` David Hildenbrand
2025-08-25 14:59               ` Mike Rapoport
2025-08-25 15:42                 ` David Hildenbrand
2025-08-25 16:17                   ` Mike Rapoport
2025-08-25 16:23                     ` David Hildenbrand
2025-08-25 16:58                       ` update kernel-doc for MEMBLOCK_RSRV_NOINIT (was: Re: [PATCH RFC 10/35] mm/hugetlb: cleanup hugetlb_folio_init_tail_vmemmap()) Mike Rapoport
2025-08-25 18:32                         ` update kernel-doc for MEMBLOCK_RSRV_NOINIT David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 11/35] mm: sanity-check maximum folio size in folio_set_order() David Hildenbrand
2025-08-21 20:36   ` Zi Yan
2025-08-21 20:06 ` [PATCH RFC 12/35] mm: limit folio/compound page sizes in problematic kernel configs David Hildenbrand
2025-08-21 20:46   ` Zi Yan
2025-08-21 20:49     ` David Hildenbrand
2025-08-21 20:50       ` Zi Yan
2025-08-24 13:24   ` Mike Rapoport
2025-08-21 20:06 ` [PATCH RFC 13/35] mm: simplify folio_page() and folio_page_idx() David Hildenbrand
2025-08-21 20:55   ` Zi Yan
2025-08-21 21:00     ` David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 14/35] mm/mm/percpu-km: drop nth_page() usage within single allocation David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 15/35] fs: hugetlbfs: remove nth_page() usage within folio in adjust_range_hwpoison() David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 16/35] mm/pagewalk: drop nth_page() usage within folio in folio_walk_start() David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 17/35] mm/gup: drop nth_page() usage within folio when recording subpages David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 18/35] io_uring/zcrx: remove "struct io_copy_cache" and one nth_page() usage David Hildenbrand
2025-08-22 11:32   ` Pavel Begunkov
2025-08-22 13:59     ` David Hildenbrand
2025-08-27  9:43       ` Pavel Begunkov
2025-08-21 20:06 ` [PATCH RFC 19/35] io_uring/zcrx: remove nth_page() usage within folio David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 20/35] mips: mm: convert __flush_dcache_pages() to __flush_dcache_folio_pages() David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 21/35] mm/cma: refuse handing out non-contiguous page ranges David Hildenbrand
2025-08-26 10:45   ` Alexandru Elisei
2025-08-26 11:04     ` David Hildenbrand
2025-08-26 13:03       ` Alexandru Elisei
2025-08-26 13:08         ` David Hildenbrand
2025-08-26 13:11           ` Alexandru Elisei
2025-08-21 20:06 ` [PATCH RFC 22/35] dma-remap: drop nth_page() in dma_common_contiguous_remap() David Hildenbrand
2025-08-22  8:15   ` Marek Szyprowski
2025-08-21 20:06 ` [PATCH RFC 23/35] scatterlist: disallow non-contigous page ranges in a single SG entry David Hildenbrand
2025-08-22  8:15   ` Marek Szyprowski
2025-08-21 20:06 ` [PATCH RFC 24/35] ata: libata-eh: drop nth_page() usage within " David Hildenbrand
2025-08-22  1:59   ` Damien Le Moal
2025-08-22  6:18     ` David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 25/35] drm/i915/gem: " David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 26/35] mspro_block: " David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 27/35] memstick: " David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 28/35] mmc: " David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 29/35] scsi: core: " David Hildenbrand
2025-08-22 18:01   ` Bart Van Assche
2025-08-22 18:10     ` David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 30/35] vfio/pci: " David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 31/35] crypto: remove " David Hildenbrand
2025-08-21 20:24   ` Linus Torvalds
2025-08-21 20:29     ` David Hildenbrand
2025-08-21 20:36       ` Linus Torvalds
2025-08-21 20:37       ` David Hildenbrand
2025-08-21 20:40       ` Linus Torvalds
2025-08-21 20:06 ` [PATCH RFC 32/35] mm/gup: drop nth_page() usage in unpin_user_page_range_dirty_lock() David Hildenbrand
2025-08-21 20:06 ` [PATCH RFC 33/35] kfence: drop nth_page() usage David Hildenbrand
2025-08-21 20:32   ` David Hildenbrand
2025-08-21 21:45     ` David Hildenbrand
2025-08-21 20:07 ` [PATCH RFC 34/35] block: update comment of "struct bio_vec" regarding nth_page() David Hildenbrand
2025-08-21 20:07 ` [PATCH RFC 35/35] mm: remove nth_page() David Hildenbrand
2025-08-21 21:37 ` [syzbot ci] " syzbot ci
2025-08-22 14:30 ` [PATCH RFC 00/35] " Jason Gunthorpe

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