linux-kernel - RE: [PATCH 3/4] ARM: drop CONFIG

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Message-ID: <d54e11cf3f4d4216b5cecf29b761cd45@AcuMS.aculab.com>
Date: Sat, 14 Dec 2024 18:40:11 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Arnd Bergmann' <arnd@...nel.org>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Arnd
 Bergmann" <arnd@...db.de>, "linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-rt-devel@...ts.linux.dev" <linux-rt-devel@...ts.linux.dev>, "Ard
 Biesheuvel" <ardb@...nel.org>, Clark Williams <clrkwllms@...nel.org>, "Jason
 Baron" <jbaron@...mai.com>, Josh Poimboeuf <jpoimboe@...nel.org>, "Linus
 Walleij" <linus.walleij@...aro.org>, Mark Rutland <mark.rutland@....com>,
	Matthew Wilcox <willy@...radead.org>, Peter Zijlstra <peterz@...radead.org>,
	Russell King <linux@...linux.org.uk>, Sebastian Andrzej Siewior
	<bigeasy@...utronix.de>, Steven Rostedt <rostedt@...dmis.org>
Subject: RE: [PATCH 3/4] ARM: drop CONFIG_HIGHPTE support

From: Arnd Bergmann
> Sent: 10 December 2024 16:06
...
> 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.

'Picking at nits' 'highmem' support was needed for systems with 4GB of RAM
in order to use more than 3GB or 3.5GB (depending on the bios) because
of the physical addresses that are reserved for PCI (and other MMIO).

	David

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