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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1756984183; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=K+KhCel/FG+KZ+Z3G+vFcuQ+ux/WwyPr/PSbZ+GFoDU=; b=MoVsxZD1TsnUUKH/018pTehr7y4ZaUS8UX38bQmsVlzgCmxQc747z2AJxqLdcjNxT8ndMX 4TCONNEGpLGHW8OdF44csqZAaj/0xjMAQKXafYboWsBKou6pTjNB+mIirPslM+m28tEJBk +1dRA8l3l3rHdLxept0RoC6RKjl3tAc= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5A24E1756; Thu, 4 Sep 2025 04:09:34 -0700 (PDT) Received: from [10.1.37.179] (XHFQ2J9959.cambridge.arm.com [10.1.37.179]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DE9E83F6A8; Thu, 4 Sep 2025 04:09:40 -0700 (PDT) Message-ID: <74603a7e-74f7-4d8f-9c2e-7caa42f2399f@arm.com> Date: Thu, 4 Sep 2025 12:09:39 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 4/6] arm64: mm: Optimize split_kernel_leaf_mapping() Content-Language: en-GB To: Catalin Marinas Cc: Will Deacon , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Yang Shi , Ard Biesheuvel , Dev Jain , scott@os.amperecomputing.com, cl@gentwo.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20250829115250.2395585-1-ryan.roberts@arm.com> <20250829115250.2395585-5-ryan.roberts@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 8B5911C000A X-Stat-Signature: t3ud865pmz3kcw6ujq618u6oqwwcerxj X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1756984183-696222 X-HE-Meta: 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 QOewZ/8D SapChrBgtRP1uRhMWtN4zOMg6C+I2NuLBjxwtuRRVB2YVmIFWcsNRWryVUf2H8QyX5vUu0qsMYomnIH9+H0UD6KBtkq+nWGsPkYHOwwvr6Vkj7UWjH4/SqbuhlbmPmHWoEYYsFz9GJWD1VQiDUcggYED682e+VxeaA3+k0KRnB4ahHpPOGleGJ5totkdbxJ+G8zz5xrulI/DeTZYlm/nja2c7y2imb+VHYdbhI4n1KUj2BKAtQRNljH7bHA== 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 03/09/2025 20:20, Catalin Marinas wrote: > On Fri, Aug 29, 2025 at 12:52:45PM +0100, Ryan Roberts wrote: >> The common case for split_kernel_leaf_mapping() is for a single page. >> Let's optimize this by only calling split_kernel_leaf_mapping_locked() >> once. >> >> Since the start and end address are PAGE_SIZE apart, they must be >> contained within the same contpte block. Further, if start is at the >> beginning of the block or end is at the end of the block, then the other >> address must be in the _middle_ of the block. So if we split on this >> middle-of-the-contpte-block address, it is guaranteed that the >> containing contpte block is split to ptes and both start and end are >> therefore mapped by pte. >> >> This avoids the second call to split_kernel_leaf_mapping_locked() >> meaning we only have to walk the pgtable once. >> >> Signed-off-by: Ryan Roberts > > Reviewed-by: Catalin Marinas > > And I agree with Yang, you can just fold this into the previous patch. Yep, will do. Thanks for the review.