linux-kernel - Re: [PATCH 2/2] mm: pgtable: remove unnecessary split ptlock for kernel PMD page

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 for Android: free password hash cracker in your pocket

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

Date: Sun, 4 Feb 2024 18:54:07 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Qi Zheng <zhengqi.arch@...edance.com>
Cc: akpm@...ux-foundation.org, arnd@...db.de, muchun.song@...ux.dev,
	david@...hat.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH 2/2] mm: pgtable: remove unnecessary split ptlock for
 kernel PMD page

On Thu, Feb 01, 2024 at 04:05:41PM +0800, Qi Zheng wrote:
> For kernel PMD entry, we use init_mm.page_table_lock to protect it, so
> there is no need to allocate and initialize the split ptlock for kernel
> PMD page.

I don't think this is a great idea.  Maybe there's no need to initialise
it, but keeping things the same between kernel & user page tables is a
usually better.  We don't normally allocate memory for the spinlock,
it's only in debugging scenarios like LOCKDEP.  I would drop this unless
you have a really compelling argument to make.