From: Lorenzo Stoakes <ljs@kernel•org>
To: "Michael S. Tsirkin" <mst@redhat•com>
Cc: linux-kernel@vger•kernel.org,
"David Hildenbrand (Arm)" <david@kernel•org>,
"Jason Wang" <jasowang@redhat•com>,
"Xuan Zhuo" <xuanzhuo@linux•alibaba.com>,
"Eugenio Pérez" <eperezma@redhat•com>,
"Muchun Song" <muchun.song@linux•dev>,
"Oscar Salvador" <osalvador@suse•de>,
"Andrew Morton" <akpm@linux-foundation•org>,
"Liam R. Howlett" <liam@infradead•org>,
"Vlastimil Babka" <vbabka@kernel•org>,
"Mike Rapoport" <rppt@kernel•org>,
"Suren Baghdasaryan" <surenb@google•com>,
"Michal Hocko" <mhocko@suse•com>,
"Brendan Jackman" <jackmanb@google•com>,
"Johannes Weiner" <hannes@cmpxchg•org>, "Zi Yan" <ziy@nvidia•com>,
"Baolin Wang" <baolin.wang@linux•alibaba.com>,
"Nico Pache" <npache@redhat•com>,
"Ryan Roberts" <ryan.roberts@arm•com>,
"Dev Jain" <dev.jain@arm•com>, "Barry Song" <baohua@kernel•org>,
"Lance Yang" <lance.yang@linux•dev>,
"Hugh Dickins" <hughd@google•com>,
"Matthew Brost" <matthew.brost@intel•com>,
"Joshua Hahn" <joshua.hahnjy@gmail•com>,
"Rakie Kim" <rakie.kim@sk•com>,
"Byungchul Park" <byungchul@sk•com>,
"Gregory Price" <gourry@gourry•net>,
"Ying Huang" <ying.huang@linux•alibaba.com>,
"Alistair Popple" <apopple@nvidia•com>,
"Christoph Lameter" <cl@gentwo•org>,
"David Rientjes" <rientjes@google•com>,
"Roman Gushchin" <roman.gushchin@linux•dev>,
"Harry Yoo" <harry.yoo@oracle•com>,
"Axel Rasmussen" <axelrasmussen@google•com>,
"Yuanchu Xie" <yuanchu@google•com>, "Wei Xu" <weixugc@google•com>,
"Chris Li" <chrisl@kernel•org>,
"Kairui Song" <kasong@tencent•com>,
"Kemeng Shi" <shikemeng@huaweicloud•com>,
"Nhat Pham" <nphamcs@gmail•com>, "Baoquan He" <bhe@redhat•com>,
virtualization@lists•linux.dev, linux-mm@kvack•org,
"Andrea Arcangeli" <aarcange@redhat•com>
Subject: Re: [PATCH v10 08/37] mm: add alloc_contig_frozen_pages_user for cache-friendly zeroing
Date: Mon, 8 Jun 2026 11:29:48 +0100 [thread overview]
Message-ID: <aiaYcZonbHSe5NfO@lucifer> (raw)
In-Reply-To: <f2036f596f17f66fb55b74a5fd85e8b7ab51876d.1780906288.git.mst@redhat.com>
On Mon, Jun 08, 2026 at 04:35:29AM -0400, Michael S. Tsirkin wrote:
> Add a _user variant of alloc_contig_frozen_pages that accepts a user_addr
> parameter for cache-friendly zeroing of contiguous allocations.
>
> No functional change; all existing callers continue to pass
> USER_ADDR_NONE.
Well, except that you're adding a new function...
>
> Note for reviewers: non-compound contiguous allocations are
Please don't put notes for reviewers in commit messages.
> zeroed via kernel_init_pages, same as before this patch.
> There is no fault address because these allocations are not
> from the page fault path. For compound allocations, user_addr
> reaches post_alloc_hook() which calls folio_zero_user() with
> the dcache flush on cache-aliasing architectures.
Yeah it's exactly this kind of 'just have to know' stuff that makes this
user_addr approach unacceptable.
We mustn't add more cognitive overhead for already confusing code. Now
everybody using these has to figure out what 'user_addr' means and will
inevitably get it wrong.
This whole approach needs to be rethought.
>
> Note about Sashiko (sashiko.dev) false positives: sashiko
> flags two issues here: (1) user_addr silently ignored for
> non-compound allocations, and (2) post_alloc_hook ignores
> user_addr. Both are false positives: (1) non-compound
> contiguous allocations have no fault address to pass, and
> (2) post_alloc_hook does use user_addr when it is not
> USER_ADDR_NONE.
Please don't put AI hallucinations in commit messages.
If you want something to not appear in a commit message, but want reviewers
to see it, put it below the '---' in the patch.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat•com>
This patch is unacceptable for the same reasons given for 7/37.
> Assisted-by: Claude:claude-opus-4-6
> ---
> include/linux/gfp.h | 6 ++++++
> mm/page_alloc.c | 42 ++++++++++++++++++++++++++++++++----------
> 2 files changed, 38 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index ee35c5367abc..73109d4e31a4 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -453,6 +453,12 @@ struct page *alloc_contig_frozen_pages_noprof(unsigned long nr_pages,
> #define alloc_contig_frozen_pages(...) \
> alloc_hooks(alloc_contig_frozen_pages_noprof(__VA_ARGS__))
>
> +struct page *alloc_contig_frozen_pages_user_noprof(unsigned long nr_pages,
> + gfp_t gfp_mask, int nid, nodemask_t *nodemask,
> + unsigned long user_addr);
> +#define alloc_contig_frozen_pages_user(...) \
> + alloc_hooks(alloc_contig_frozen_pages_user_noprof(__VA_ARGS__))
> +
> struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_mask,
> int nid, nodemask_t *nodemask);
> #define alloc_contig_pages(...) \
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 21b52c879751..6d3f284c607d 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6975,13 +6975,15 @@ static void __free_contig_frozen_range(unsigned long pfn, unsigned long nr_pages
> }
>
> /**
> - * alloc_contig_frozen_range() -- tries to allocate given range of frozen pages
> + * __alloc_contig_frozen_range() -- tries to allocate given range of frozen pages
> * @start: start PFN to allocate
> * @end: one-past-the-last PFN to allocate
> * @alloc_flags: allocation information
> * @gfp_mask: GFP mask. Node/zone/placement hints are ignored; only some
> * action and reclaim modifiers are supported. Reclaim modifiers
> * control allocation behavior during compaction/migration/reclaim.
> + * @user_addr: user virtual address for cache-friendly zeroing, or
> + * USER_ADDR_NONE for kernel allocations.
Yeah, I really do not want us passing USER_ADDR_NONE for kernel allocations
thanks. This is hugely confusing already pretty confusing logic.
> *
> * The PFN range does not have to be pageblock aligned. The PFN range must
> * belong to a single zone.
> @@ -6997,8 +6999,9 @@ static void __free_contig_frozen_range(unsigned long pfn, unsigned long nr_pages
> *
> * Return: zero on success or negative error code.
> */
> -int alloc_contig_frozen_range_noprof(unsigned long start, unsigned long end,
> - acr_flags_t alloc_flags, gfp_t gfp_mask)
> +static int __alloc_contig_frozen_range(unsigned long start, unsigned long end,
> + acr_flags_t alloc_flags, gfp_t gfp_mask,
> + unsigned long user_addr)
> {
> const unsigned int order = ilog2(end - start);
> unsigned long outer_start, outer_end;
> @@ -7125,7 +7128,7 @@ int alloc_contig_frozen_range_noprof(unsigned long start, unsigned long end,
> struct page *head = pfn_to_page(start);
>
> check_new_pages(head, order);
> - prep_new_page(head, order, gfp_mask, 0, USER_ADDR_NONE);
> + prep_new_page(head, order, gfp_mask, 0, user_addr);
> } else {
> ret = -EINVAL;
> WARN(true, "PFN range: requested [%lu, %lu), allocated [%lu, %lu)\n",
> @@ -7135,6 +7138,13 @@ int alloc_contig_frozen_range_noprof(unsigned long start, unsigned long end,
> undo_isolate_page_range(start, end);
> return ret;
> }
> +
> +int alloc_contig_frozen_range_noprof(unsigned long start, unsigned long end,
> + acr_flags_t alloc_flags, gfp_t gfp_mask)
> +{
> + return __alloc_contig_frozen_range(start, end, alloc_flags, gfp_mask,
> + USER_ADDR_NONE);
> +}
> EXPORT_SYMBOL(alloc_contig_frozen_range_noprof);
>
> /**
> @@ -7227,14 +7237,16 @@ static bool zone_spans_last_pfn(const struct zone *zone,
> return zone_spans_pfn(zone, last_pfn);
> }
>
> -/**
> - * alloc_contig_frozen_pages() -- tries to find and allocate contiguous range of frozen pages
> +/*
> + * alloc_contig_frozen_pages_user_noprof() -- allocate contiguous frozen pages with user address
> * @nr_pages: Number of contiguous pages to allocate
> * @gfp_mask: GFP mask. Node/zone/placement hints limit the search; only some
> * action and reclaim modifiers are supported. Reclaim modifiers
> * control allocation behavior during compaction/migration/reclaim.
> * @nid: Target node
> * @nodemask: Mask for other possible nodes
> + * @user_addr: user virtual address for cache-friendly zeroing, or
> + * USER_ADDR_NONE for kernel allocations.
> *
> * This routine is a wrapper around alloc_contig_frozen_range(). It scans over
> * zones on an applicable zonelist to find a contiguous pfn range which can then
> @@ -7253,8 +7265,9 @@ static bool zone_spans_last_pfn(const struct zone *zone,
> *
> * Return: pointer to contiguous frozen pages on success, or NULL if not successful.
> */
> -struct page *alloc_contig_frozen_pages_noprof(unsigned long nr_pages,
> - gfp_t gfp_mask, int nid, nodemask_t *nodemask)
> +struct page *alloc_contig_frozen_pages_user_noprof(unsigned long nr_pages,
> + gfp_t gfp_mask, int nid, nodemask_t *nodemask,
> + unsigned long user_addr)
> {
> unsigned long ret, pfn, flags;
> struct zonelist *zonelist;
> @@ -7282,10 +7295,11 @@ struct page *alloc_contig_frozen_pages_noprof(unsigned long nr_pages,
> * win the race and cause allocation to fail.
> */
> spin_unlock_irqrestore(&zone->lock, flags);
> - ret = alloc_contig_frozen_range_noprof(pfn,
> + ret = __alloc_contig_frozen_range(pfn,
> pfn + nr_pages,
> ACR_FLAGS_NONE,
> - gfp_mask);
> + gfp_mask,
> + user_addr);
> if (!ret)
> return pfn_to_page(pfn);
> spin_lock_irqsave(&zone->lock, flags);
> @@ -7307,6 +7321,14 @@ struct page *alloc_contig_frozen_pages_noprof(unsigned long nr_pages,
> }
> return NULL;
> }
> +EXPORT_SYMBOL(alloc_contig_frozen_pages_user_noprof);
Generally we don't add EXPORT_SYMBOL() for new stuff unless
unavoidable. EXPORT_SYMBOL_GPL() is preferred.
> +
> +struct page *alloc_contig_frozen_pages_noprof(unsigned long nr_pages,
> + gfp_t gfp_mask, int nid, nodemask_t *nodemask)
> +{
> + return alloc_contig_frozen_pages_user_noprof(nr_pages, gfp_mask, nid,
> + nodemask, USER_ADDR_NONE);
> +}
> EXPORT_SYMBOL(alloc_contig_frozen_pages_noprof);
>
> /**
> --
> MST
>
Thanks, Lorenzo
next prev parent reply other threads:[~2026-06-08 10:30 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-08 8:33 [PATCH v10 00/37] mm/virtio: skip redundant zeroing of host-zeroed pages Michael S. Tsirkin
2026-06-08 8:34 ` [PATCH v10 01/37] mm: mempolicy: fix interleave index calculation Michael S. Tsirkin
2026-06-08 9:43 ` Lorenzo Stoakes
2026-06-08 8:34 ` [PATCH v10 02/37] mm: memory-failure: serialize TestSetPageHWPoison with zone->lock Michael S. Tsirkin
2026-06-08 9:43 ` Lorenzo Stoakes
2026-06-08 13:48 ` Michael S. Tsirkin
2026-06-08 14:14 ` Lorenzo Stoakes
2026-06-08 16:20 ` Andrew Morton
2026-06-08 8:34 ` [PATCH v10 03/37] mm: page_alloc: propagate PageReported flag across buddy splits Michael S. Tsirkin
2026-06-08 9:52 ` Lorenzo Stoakes
2026-06-08 12:50 ` Matthew Wilcox
2026-06-08 8:34 ` [PATCH v10 04/37] mm: page_reporting: allow driver to set batch capacity Michael S. Tsirkin
2026-06-08 8:34 ` [PATCH v10 05/37] mm: hugetlb: remove dead alloc_hugetlb_folio stub Michael S. Tsirkin
2026-06-08 9:56 ` Lorenzo Stoakes
2026-06-08 8:35 ` [PATCH v10 06/37] mm: move vma_alloc_folio_noprof to page_alloc.c Michael S. Tsirkin
2026-06-08 10:05 ` Lorenzo Stoakes
2026-06-08 8:35 ` [PATCH v10 07/37] mm: thread user_addr through page allocator for cache-friendly zeroing Michael S. Tsirkin
2026-06-08 10:23 ` Lorenzo Stoakes
2026-06-08 11:06 ` Lorenzo Stoakes
2026-06-08 13:04 ` Matthew Wilcox
2026-06-08 13:09 ` Lorenzo Stoakes
2026-06-08 14:26 ` David Hildenbrand (Arm)
2026-06-08 14:31 ` Matthew Wilcox
2026-06-08 14:37 ` David Hildenbrand (Arm)
2026-06-08 14:44 ` Matthew Wilcox
2026-06-08 14:55 ` David Hildenbrand (Arm)
2026-06-08 11:08 ` David Hildenbrand (Arm)
2026-06-08 15:27 ` Zi Yan
2026-06-08 8:35 ` [PATCH v10 08/37] mm: add alloc_contig_frozen_pages_user " Michael S. Tsirkin
2026-06-08 10:29 ` Lorenzo Stoakes [this message]
2026-06-08 8:35 ` [PATCH v10 09/37] mm: hugetlb: thread user_addr through gigantic page allocation Michael S. Tsirkin
2026-06-08 8:36 ` [PATCH v10 10/37] mm: add folio_zero_user stub for configs without THP/HUGETLBFS Michael S. Tsirkin
2026-06-08 9:12 ` Lorenzo Stoakes
2026-06-08 8:36 ` [PATCH v10 11/37] mm: page_alloc: move prep_compound_page before post_alloc_hook Michael S. Tsirkin
2026-06-08 10:33 ` Lorenzo Stoakes
2026-06-08 8:36 ` [PATCH v10 12/37] mm: use folio_zero_user for user pages in post_alloc_hook Michael S. Tsirkin
2026-06-08 11:23 ` Lorenzo Stoakes
2026-06-08 15:53 ` Gregory Price
2026-06-08 8:36 ` [PATCH v10 13/37] mm: use __GFP_ZERO in vma_alloc_zeroed_movable_folio Michael S. Tsirkin
2026-06-08 10:39 ` Lorenzo Stoakes
2026-06-08 10:55 ` Lorenzo Stoakes
2026-06-08 8:37 ` [PATCH v10 14/37] mm: remove arch vma_alloc_zeroed_movable_folio overrides Michael S. Tsirkin
2026-06-08 11:29 ` Lorenzo Stoakes
2026-06-08 8:37 ` [PATCH v10 15/37] mm: alloc_anon_folio: pass raw fault address to vma_alloc_folio Michael S. Tsirkin
2026-06-08 11:35 ` Lorenzo Stoakes
2026-06-08 8:37 ` [PATCH v10 16/37] mm: alloc_swap_folio: " Michael S. Tsirkin
2026-06-08 11:37 ` Lorenzo Stoakes
2026-06-08 15:59 ` Gregory Price
2026-06-08 8:37 ` [PATCH v10 17/37] mm: page_reporting: skip redundant zeroing of host-zeroed reported pages Michael S. Tsirkin
2026-06-08 12:00 ` Lorenzo Stoakes
2026-06-08 16:09 ` Gregory Price
2026-06-08 8:38 ` [PATCH v10 18/37] mm: page_alloc: use aliasing checks instead of user_alloc_needs_zeroing Michael S. Tsirkin
2026-06-08 11:39 ` Lorenzo Stoakes
2026-06-08 8:38 ` [PATCH v10 19/37] mm: page_alloc: clear PG_zeroed on buddy merge if not both zero Michael S. Tsirkin
2026-06-08 11:47 ` Lorenzo Stoakes
2026-06-08 8:38 ` [PATCH v10 20/37] mm: page_alloc: preserve PG_zeroed in page_del_and_expand Michael S. Tsirkin
2026-06-08 8:38 ` [PATCH v10 21/37] mm: page_alloc: propagate PG_zeroed in split_large_buddy Michael S. Tsirkin
2026-06-08 8:38 ` [PATCH v10 22/37] mm: add free_frozen_pages_zeroed Michael S. Tsirkin
2026-06-08 12:06 ` Lorenzo Stoakes
2026-06-08 8:38 ` [PATCH v10 23/37] mm: page_alloc: skip kernel_init_pages for FPI_ZEROED when safe Michael S. Tsirkin
2026-06-08 12:18 ` Lorenzo Stoakes
2026-06-08 8:38 ` [PATCH v10 24/37] mm: add put_page_zeroed and folio_put_zeroed Michael S. Tsirkin
2026-06-08 12:25 ` Lorenzo Stoakes
2026-06-08 12:46 ` David Hildenbrand (Arm)
2026-06-08 14:08 ` Michael S. Tsirkin
2026-06-08 14:28 ` David Hildenbrand (Arm)
2026-06-08 8:39 ` [PATCH v10 25/37] mm: use __GFP_ZERO in alloc_anon_folio Michael S. Tsirkin
2026-06-08 12:29 ` Lorenzo Stoakes
2026-06-08 8:39 ` [PATCH v10 26/37] mm: vma_alloc_anon_folio_pmd: pass raw fault address to vma_alloc_folio Michael S. Tsirkin
2026-06-08 12:30 ` Lorenzo Stoakes
2026-06-08 8:39 ` [PATCH v10 27/37] mm: use __GFP_ZERO in vma_alloc_anon_folio_pmd Michael S. Tsirkin
2026-06-08 12:32 ` Lorenzo Stoakes
2026-06-08 8:39 ` [PATCH v10 28/37] mm: hugetlb: add gfp parameter and skip zeroing for zeroed pages Michael S. Tsirkin
2026-06-08 12:44 ` Lorenzo Stoakes
2026-06-08 8:39 ` [PATCH v10 29/37] mm: memfd: skip zeroing for zeroed hugetlb pool pages Michael S. Tsirkin
2026-06-08 12:47 ` Lorenzo Stoakes
2026-06-08 8:39 ` [PATCH v10 30/37] mm: page_reporting: add per-page zeroed bitmap for host feedback Michael S. Tsirkin
2026-06-08 8:39 ` [PATCH v10 31/37] virtio_balloon: submit reported pages as individual buffers Michael S. Tsirkin
2026-06-08 8:40 ` [PATCH v10 32/37] virtio_balloon: disable indirect descriptors Michael S. Tsirkin
2026-06-08 8:40 ` [PATCH v10 33/37] mm: page_reporting: add flush parameter with page budget Michael S. Tsirkin
2026-06-08 8:40 ` [PATCH v10 34/37] virtio_balloon: skip zeroing for host-zeroed reported pages Michael S. Tsirkin
2026-06-08 8:40 ` [PATCH v10 35/37] virtio_balloon: disable reporting zeroed optimization for confidential guests Michael S. Tsirkin
2026-06-08 8:40 ` [PATCH v10 36/37] mm: balloon: use put_page_zeroed for zeroed balloon pages Michael S. Tsirkin
2026-06-08 11:10 ` David Hildenbrand (Arm)
2026-06-08 8:40 ` [PATCH v10 37/37] virtio_balloon: implement VIRTIO_BALLOON_F_DEVICE_INIT_ON_INFLATE Michael S. Tsirkin
2026-06-08 9:17 ` [PATCH v10 00/37] mm/virtio: skip redundant zeroing of host-zeroed pages Lorenzo Stoakes
2026-06-08 12:52 ` Lorenzo Stoakes
2026-06-08 11:02 ` Vlastimil Babka (SUSE)
2026-06-08 11:13 ` Vlastimil Babka (SUSE)
2026-06-08 15:45 ` Gregory Price
2026-06-08 17:50 ` Lorenzo Stoakes
2026-06-08 14:21 ` Matthew Wilcox
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