linux-kernel - Re: [v6 04/15] mm/huge_memory: implement device-private THP splitting

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b0bd326a-0ef6-4c72-ae25-3faff1fd6eb7@redhat.com>
Date: Thu, 25 Sep 2025 12:01:36 +0200
From: David Hildenbrand <david@...hat.com>
To: Balbir Singh <balbirs@...dia.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Cc: damon@...ts.linux.dev, dri-devel@...ts.freedesktop.org,
 Zi Yan <ziy@...dia.com>, Joshua Hahn <joshua.hahnjy@...il.com>,
 Rakie Kim <rakie.kim@...com>, Byungchul Park <byungchul@...com>,
 Gregory Price <gourry@...rry.net>, Ying Huang
 <ying.huang@...ux.alibaba.com>, Alistair Popple <apopple@...dia.com>,
 Oscar Salvador <osalvador@...e.de>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Nico Pache <npache@...hat.com>,
 Ryan Roberts <ryan.roberts@....com>, Dev Jain <dev.jain@....com>,
 Barry Song <baohua@...nel.org>, Lyude Paul <lyude@...hat.com>,
 Danilo Krummrich <dakr@...nel.org>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Ralph Campbell <rcampbell@...dia.com>,
 Mika Penttilä <mpenttil@...hat.com>,
 Matthew Brost <matthew.brost@...el.com>,
 Francois Dugast <francois.dugast@...el.com>
Subject: Re: [v6 04/15] mm/huge_memory: implement device-private THP splitting

On 16.09.25 14:21, Balbir Singh wrote:
> Add support for splitting device-private THP folios, enabling fallback
> to smaller page sizes when large page allocation or migration fails.
> 
> Key changes:
> - split_huge_pmd(): Handle device-private PMD entries during splitting
> - Preserve RMAP_EXCLUSIVE semantics for anonymous exclusive folios
> - Skip RMP_USE_SHARED_ZEROPAGE for device-private entries as they
>    don't support shared zero page semantics
> 
> Signed-off-by: Balbir Singh <balbirs@...dia.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Zi Yan <ziy@...dia.com>
> Cc: Joshua Hahn <joshua.hahnjy@...il.com>
> Cc: Rakie Kim <rakie.kim@...com>
> Cc: Byungchul Park <byungchul@...com>
> Cc: Gregory Price <gourry@...rry.net>
> Cc: Ying Huang <ying.huang@...ux.alibaba.com>
> Cc: Alistair Popple <apopple@...dia.com>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> Cc: Nico Pache <npache@...hat.com>
> Cc: Ryan Roberts <ryan.roberts@....com>
> Cc: Dev Jain <dev.jain@....com>
> Cc: Barry Song <baohua@...nel.org>
> Cc: Lyude Paul <lyude@...hat.com>
> Cc: Danilo Krummrich <dakr@...nel.org>
> Cc: David Airlie <airlied@...il.com>
> Cc: Simona Vetter <simona@...ll.ch>
> Cc: Ralph Campbell <rcampbell@...dia.com>
> Cc: Mika Penttilä <mpenttil@...hat.com>
> Cc: Matthew Brost <matthew.brost@...el.com>
> Cc: Francois Dugast <francois.dugast@...el.com>
> ---
>   mm/huge_memory.c | 138 +++++++++++++++++++++++++++++++++--------------
>   1 file changed, 98 insertions(+), 40 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 78166db72f4d..5291ee155a02 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2872,16 +2872,18 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
>   	struct page *page;
>   	pgtable_t pgtable;
>   	pmd_t old_pmd, _pmd;
> -	bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false;
> -	bool anon_exclusive = false, dirty = false;
> +	bool soft_dirty, uffd_wp = false, young = false, write = false;
> +	bool anon_exclusive = false, dirty = false, present = false;
>   	unsigned long addr;
>   	pte_t *pte;
>   	int i;
> +	swp_entry_t swp_entry;

Not renaming this variable avoids a lot of churn below. So please keep 
it called "entry" in this patch.

-- 
Cheers

David / dhildenb