From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793197029; b=y7BuU+LjgGDZ0d7d/UjAal+5wQb97Lynkp7a19W+hR1mHYk2UeRh5VjdVVXDnt3MrHki TGzEp3qNzovkP/VHgoBgrwatuQr+uDW1KiZfIo4e1mOnUEORnrGaeqw9AA2IwMNYo30BW m+Xl6arSi5qZDqkv5cek1HRTbQ9GY0FMwVHoMbfcCkhG64HbMKNy74L7pjFGAFxFKVl3/ CCyZAneU6SHe9t8KQyBo/VaC0udWhbH+36+0JyYzmPmUiSNi0O/0L7+2ocx0NNEK5NEnS ATgJy7+93405XkhvIw9FX37CyYlPdxLxFr14oJFrZo8cGy2Sna6XA8YRl8TGeAFHGoA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793197029; h=Received:DKIM-Signature:Received:Received:X-ME-Sender:X-ME-Received: X-ME-Proxy-Cause:X-ME-Proxy:Feedback-ID:Received:Date:From:To:Cc: Subject:Message-ID:References:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; bh=KjE+Uii9HdIaARV62zaMQ61CIuncPf7bH8UJ3pdaQYA=; b=FVFpMgXnUv5iekdJDoTzdBWpPl+AL/mfuUPX5REmtviW0n6DXJP2t/C0tOelKgUh6gCl eZfIgaFUoQBDOZxEpEk+4j4rYSTlagE0bl5cVTLWmTxK41H5e2vXb403shq3bFKQXBwVM I7YFxgAxDbOH13X5hTlhIbYsxeFO3/2qxwEmfffZsz4knmHaMK/yYwtE+idwERW3jnI2G HYFYKx/CTaOTEdl57JfoRQVFGzlBbGNryME2l8fI2JRLRtinJPvXcsLNh1Y9p0GE+3Lqe K0bnERddEUQ14APotmoS+Fc9zVAyFSoLsqqgVtz87vbXQktxX+R6/dNDv8tQiR6XXmQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Zcdh2eIB; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1C69F606A31C; Wed, 28 Oct 2026 14:17:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Zcdh2eIB Received: by smtp.kernel.org (Postfix) with ESMTPSA id E9A281F01828; Wed, 28 Oct 2026 14:17:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793197028; bh=KjE+Uii9HdIaARV62zaMQ61CIuncPf7bH8UJ3pdaQYA=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Zcdh2eIBUKC4hwGul8m2X99COtLyRxU9I1tM3K8HNMrbYYnTTWhdHlgLZ8oc9hQ0E hkij64PMlw2B35u30Io3tH3HsD0bNhhXsgX59QJdkIQoqrmwecSDeQzG4blmv9KCKs zpbyI7gIirKXkwF2M7UlINaw/GRVFmWIbS7pSH3TIHgpDG7aJwpWbBcAaNwEJGxUg/ UUvr1CGfqhw8l0QXJXNBe42SvHDAw91meYdE2y4qqF/osXsIl4NB3bv5lDIrCwlYfD WJwEisb3g4Fv+JB51XtPrQYsW8TA6hHI6AdqdFh3MOkHtw1CHYKUBb2HdzBgS8AyGI CnOSlmOc8ymzQ== Received: from phl-compute-02.internal (phl-compute-02.internal [10.202.2.42]) by mailfauth.ams.internal (Postfix) with ESMTP id D36591980047; Wed, 28 Oct 2026 10:17:00 -0400 (EDT) Received: from phl-frontend-03 ([10.202.2.162]) by phl-compute-02.internal (MEProxy); Wed, 28 Oct 2026 10:17:05 -0400 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: dmFkZTFBUCDrd/5ordvcAtkU6JjR9vrPimb+UYxK8G9IVcsl+hsz6Ui5my93/MGWrjS87u fXqSgPXckr17WjUL+tJxx9X6tIeCr9bfJMhwSdRRpKBvQHhzUHHeuF90VW3GvmiAwMBcQx Rf2Yec/qkpxdmRN0gn81nfMEtgtzr9xle+Sqvm4msx4Gu47eXQusCRI+UTCHDaQLpM88Zw rA2KSpwrrNtwy3hNsymytz/3zQf5zrQhLIfZgGCnRsgT13HdYXLGRb5Hfufh9/xN00Sw7j VoUYeEMtfP62ZRJRgpiIZ1sb8H4pSmNadcRIVzTJpNxYLEIHjCh6+OIkfWTl5h6WIw54gA KE6JNmsl7DeQ0Kg8mW/mO/uEfAd5ourm2uLsVrQyqhxYxZW46VXJE/JyALAdTsn4tHLHQR 9J3XB/OTW36iz9yadG/flUPik6iZcWFmEGKzsegO1g5puDzneN2xiaetmpoWF0UM5wnKqK MFQ06f2mDmplk9n8JKhi5ClQ5Fqm71Y2Jgt/24wpthhs2MF+1PFVTNqTJDk2AJWHnLl5y8 ++hBW9M77S9dYUxy+BMYF15QXjLxOsg3nNoK+b02p8kN9M/KDQpW6b5xHKMmV9hna2Qdc4 F2kZ6V+Uw0HniFG7WD/kBET6ZxUz0YZm4Xr7zmI/BK6THBFe4X3S7pitIvXA X-ME-Proxy: Feedback-ID: i10464835:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Wed, 28 Oct 2026 10:16:59 -0400 (EDT) Date: Wed, 28 Oct 2026 14:16:58 +0000 From: Kiryl Shutsemau To: Peter Zijlstra Cc: Muchun Song , "David Hildenbrand (Arm)" , Andrew Morton , Matthew Wilcox , Usama Arif , Frank van der Linden , Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Zi Yan , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , Huacai Chen , WANG Xuerui , Palmer Dabbelt , Paul Walmsley , Albert Ou , Alexandre Ghiti , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, Dave Hansen , Andy Lutomirski Subject: Re: [PATCHv7 13/18] mm: Drop fake head checks Message-ID: References: <070DDE5C-2183-4A8B-AC2D-891CAE15E581@linux.dev> <4A32F5E6-977D-4720-8723-B19AFBC08FCF@linux.dev> <7cb3dd91-f518-49b6-b311-9ec807b3c63b@linux.dev> <20261028080635.GD2668804@noisy.programming.kicks-ass.net> <20261028133439.GK2668804@noisy.programming.kicks-ass.net> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261028133439.GK2668804@noisy.programming.kicks-ass.net> On Wed, Oct 28, 2026 at 02:34:39PM +0100, Peter Zijlstra wrote: > > Only architectures with HVO matter here: x86-64, riscv and loongarch. > > arm64 has had it disabled since 060a2c92d1b6. > > Per that commit, could it be re-enabled now that its no longer marked RO? No. The problem there is the PFN change on a live vmemmap PTE, which needs break-before-make on arm64. Dropping RO only removes the permission change. James Houghton is working on it with an Access Flag trick: https://lore.kernel.org/r/20261003002123.505555-1-jthoughton@google.com arm64 will need the writable tail too: its atomic_fetch_add_unless() is a CAS loop. -- Kiryl Shutsemau / Kirill A. Shutemov