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bh=JniKxZaKIckwpZT/I3NSeEVGJX/9DihSJgU5m9ylrJY=; b=oZ3V66Sew7gClffQOrHqY78VWXJUbUzqFXHLdb6mAJUHtN2lM53BRX0HxOUm21QQDlSmIH r2Ka4+RbT0M60LM3aE+tOiVwbNWJptwi+foi/VMCODdUgV60nNKhYtMPiBiCZJ3+Aadwuo n01zz9i0K1crpJHShTz83I6JmdMyw76zmLNbbqUPBDHmCbydd0cDAwFVRnHT9NOxM7++77 4oZN6WBmzSPwKY2UPo38UjvNSx5un1kF5593+Ab9mC3RoZghFEXjR8kahVmgPkknbVNrBA kmZuBQiND+pNNb/1mE+4GpqyYThyVarfjAaNZ4VxZKr30fb19DyElD/6DjObXQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1733927119; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=JniKxZaKIckwpZT/I3NSeEVGJX/9DihSJgU5m9ylrJY=; b=d7+F9tU81J6PP0W/cr25Ib9q5pTZelDPbjs7enEICI6UojHUyU8/5vvl8k9YB0rsU4bX1d LahZ3EQ1IsluJFAA== From: Sebastian Andrzej Siewior To: Arnd Bergmann Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Arnd Bergmann , linux-mm@kvack.org, linux-rt-devel@lists.linux.dev, Ard Biesheuvel , Clark Williams , Jason Baron , Josh Poimboeuf , Linus Walleij , Mark Rutland , Matthew Wilcox , Peter Zijlstra , Russell King , Steven Rostedt Subject: Re: [PATCH 3/4] ARM: drop CONFIG_HIGHPTE support Message-ID: <20241211142517.fhnOz46I@linutronix.de> References: <20241210160556.2341497-1-arnd@kernel.org> <20241210160556.2341497-4-arnd@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20241210160556.2341497-4-arnd@kernel.org> X-Stat-Signature: x53wj9gjw3x6czmhafbodiua1dbf7y3z X-Rspamd-Queue-Id: BAA731A0015 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1733927096-895827 X-HE-Meta: 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 5F15NX0/ sj7JyFzSZ6Q9qr4pjm0D2KhHKaSLx6XxWGTGqNm2ttjgPi41hry5cb6DVjMvpVIcc9TyfbKXfEQPL63mU+o4k3nal4mR78/aTgUaJZyHOhQyMrFplqWpAb5DLHyqY2q/9GDlDU+KqWma13XB6zMldKbUPFOa1vGa8pg46AhtH6nh+nvB85MyzrEFBMrmOitfDfKVpU/PXztrkcvhzibfNsUSqywfwC2S6n3geyuGxTQFQpkc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2024-12-10 17:05:55 [+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. Based on what I have written in 20241211140402.yf7gMExr@linutronix.de it makes sense. Acked-by: Sebastian Andrzej Siewior Sebastian