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h=Date:From:To:Cc:Subject:References:In-Reply-To; b=cfI/L2eY2qjwVL7APHC67QJOIGk/JNOUabcKBMNTHVN19Rcz72eUV6Yh3y5Ea/LHZ z5QbQ0lofex0YKPkP/CrCot0WtLB3Iun9cb9TpGzWGq7i0diBi7RiTfH+PMAtEzL2+ C0j/tS7srsbkDAQQkLK7ashTa4LxtBlawzOcVQduTw15A7JC0FoBx70BE+lVHeY9Dq c07fq9ZOjzPKmREqLefO5blbiTlVapyN80u0xRg/xm4Y01ZY7klw7sdg1ydyXEPskb 46DP+YMZNRJ2jvH8liJQifBhGUdO/X8ERo88dTaNWRmserH3XKGKSg7PzJ1GdT/0k3 sU3CZpk80JuTg== Date: Fri, 13 Nov 2026 18:41:52 +0000 From: "Lorenzo Stoakes (ARM)" To: Arnd Bergmann Cc: linux-mm@kvack.org, Arnd Bergmann , Andrew Morton , Andreas Larsson , "Christophe Leroy (CS GROUP)" , Dave Hansen , "David Hildenbrand (Arm)" , Jason Gunthorpe , Linus Walleij , Matthew Wilcox , Malin Jonsson , Richard Weinberger , Russell King , linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org Subject: Re: [PATCH v2 3/6] ARM: drop CONFIG_HIGHPTE support Message-ID: References: <20261112112528.1116405-1-arnd@kernel.org> <20261112112528.1116405-4-arnd@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261112112528.1116405-4-arnd@kernel.org> X-Stat-Signature: pjnos565aodko6dy8ksef76fek4shi8a X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 659A8180007 X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1794595320-130487 X-HE-Meta: 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 xKilae5N rZwohI5jGCWObROMeuIsCzv5ehVX2dCUilgI+tjDk7+Y039h5VV/rL6Ed7vYQrEPTRs7VIJyGKhjwZxa+696uLb7WhPwn4d7WBicNryVeNDJT4ZVSmHp3b08SKSq/ewUX2wlDIKbRfrM1VS5kIWLBprOsA3FBoiFbTg/YQprcfwQjiMP8nFevPhR62szMHEz7dQUIBnY5vQ07VtrPOTheILQHrjL0k9zILhlPCdD0pB4M/5YK109rhH5+PHiGjOaKf4GQB3cJc6ikSFqZMF5uHz6W3PJv7VHzoiaslxvBwmkj8FgZ4e20CZBRi1db7VNGHTM6 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, Nov 12, 2026 at 12:25:25PM +0100, Arnd Bergmann wrote: > From: Arnd Bergmann > > CONFIG_HIGHPTE was added in linux-2.6.32, a few years before 64-bit > support. At the time it made sense, as the CONFIG_ARM_LPAE option allowed > systems with 16GB of memory that made lowmem a particularly scarce > resource, and the HIGHPTE implementation gave feature parity with 32-bit > x86 and frv machines. > > Since Arm is the last architecture remaining that uses this, and almost > no 32-bit machines support more than 4GB of RAM, the cost of continuing > to maintain HIGHPTE seems unjustified, so remove it here to allow > simplifying the generic page table handling. > > Link: https://lore.kernel.org/lkml/20241204103042.1904639-8-arnd@kernel.org/T/#u > Signed-off-by: Arnd Bergmann > --- > I sent a patch to drop HIGHPTE support on x86 today, see > https://lore.kernel.org/lkml/20241210144945.2325330-9-arnd@kernel.org/T/#u > > If that one gets merged, we can merge this one instead of the one > that makes HIGHPTE depend on !PREEMPT_RT, but if we decide against > the x86 change, then we probably don't want this one either. > > Signed-off-by: Arnd Bergmann With Mike's change applied, LGTM and: Acked-by: Lorenzo Stoakes (ARM) > --- > arch/arm/Kconfig | 11 ----------- > arch/arm/include/asm/pgalloc.h | 8 +------- > 2 files changed, 1 insertion(+), 18 deletions(-) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index fd01ccab9c12..fc66d52d847e 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -1225,17 +1225,6 @@ config HIGHMEM > > If unsure, say n. > > -config HIGHPTE > - bool "Allocate 2nd-level pagetables from highmem" if EXPERT > - depends on HIGHMEM && !PREEMPT_RT > - default y > - help > - The VM uses one page of physical memory for each page table. > - For systems with a lot of processes, this can use a lot of > - precious low memory, eventually leading to low memory being > - consumed by page tables. Setting this option will allow > - user-space 2nd level page tables to reside in high memory. > - > config ARM_PAN > bool "Enable privileged no-access" > depends on MMU > diff --git a/arch/arm/include/asm/pgalloc.h b/arch/arm/include/asm/pgalloc.h > index a17f01235c29..ef6cb3e6d179 100644 > --- a/arch/arm/include/asm/pgalloc.h > +++ b/arch/arm/include/asm/pgalloc.h > @@ -85,18 +85,12 @@ pte_alloc_one_kernel(struct mm_struct *mm) > return pte; > } > > -#ifdef CONFIG_HIGHPTE > -#define PGTABLE_HIGHMEM __GFP_HIGHMEM > -#else > -#define PGTABLE_HIGHMEM 0 > -#endif > - > static inline pgtable_t > pte_alloc_one(struct mm_struct *mm) > { > struct page *pte; > > - pte = __pte_alloc_one(mm, GFP_PGTABLE_USER | PGTABLE_HIGHMEM); > + pte = __pte_alloc_one(mm, GFP_PGTABLE_USER); > if (!pte) > return NULL; > if (!PageHighMem(pte)) > -- > 2.53.0 > -- Cheers, Lorenzo