linux-kernel - Re: [PATCH v17 00/12] Support page table check on PowerPC

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Message-ID: <336c0402c59363956d0c4eefc1b8a059e1fcc8e4.camel@linux.ibm.com>
Date: Fri, 26 Sep 2025 08:42:35 +1000
From: Andrew Donnellan <ajd@...ux.ibm.com>
To: linuxppc-dev@...ts.ozlabs.org, linux-mm@...ck.org
Cc: akpm@...ux-foundation.org, x86@...nel.org, linux-riscv@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        pasha.tatashin@...een.com, sweettea-kernel@...miny.me,
        nicholas@...ux.ibm.com, christophe.leroy@...roup.eu,
        alexghiti@...osinc.com
Subject: Re: [PATCH v17 00/12] Support page table check on PowerPC

Hi Andrew,

On Tue, 2025-09-09 at 19:13 +1000, Andrew Donnellan wrote:
> Support page table check on all PowerPC platforms. This works by serialising
> assignments, reassignments and clears of page table entries at each level in
> order to ensure that anonymous mappings have at most one writable consumer,
> and likewise that file-backed mappings are not simultaneously also anonymous
> mappings.
> 
> In order to support this infrastructure, a number of helpers or stubs must be
> defined or updated for all powerpc platforms. Additionally, we separate
> set_pte_at() and set_pte_at_unchecked(), to allow for internal, uninstrumented
> mappings.
> 
> On some PowerPC platforms, implementing {pte,pmd,pud}_user_accessible_page()
> requires the address. We revert previous changes that removed the address
> parameter from various interfaces, and add it to some other interfaces,
> in order to allow this.
> 
> Note that on 32 bit systems with CONFIG_KFENCE=y, you need [0] to avoid
> possible failures in init code (this is a code patching/static keys issue,
> which was discovered by a user testing this series but isn't a bug in page
> table check).
> 
> (This series was initially written by Rohan McLure, who has left IBM and
> is no longer working on powerpc.)

Is this likely to make it in in time for 6.18, or should I respin it post merge
window?

Thanks,
Andrew

-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd@...ux.ibm.com   IBM Australia Limited