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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1767823719; 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:dkim-signature; bh=Leg1NekVj34gHkDnfNWZo69lYGmnkkGlrerd3elLd1w=; b=2koKbYC1mCW7/WsQyfubnthyh8IaqPcE6lhCP/gR0ZxJQwfQtbCS+7S6UpgW1NyNbXUjsz 0lBTB6x0D1BS19+oBTyrPYALXaz93r/gqobsXpyQ5CoOaYeeyrzxHxIq6eUX37EZOa/UJu gsLqGdzwhyiYrzqG5rHRZ9Lazy6+dEQ= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 8994B403D8; Wed, 7 Jan 2026 22:08:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3FF4CC4CEF1; Wed, 7 Jan 2026 22:08:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767823717; bh=EcHgfTbO7t8VeiVyN3BO6yckGe86xkojloHqHLnPFn0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=tRhx72pBwsDHXcMyUxJK2Z+HZ4xif+ezAPWVZHdUB2P2EiXRZMNhsX7UgckOW3NJR qkfrP7Gtie3R9wpWE6N78gEWzDCRsmMBlMEPSpDy6l2m5jxeCz/zgcTkK7Sazda6wv G+chKPR3nFMgYWaixGJ4y8EeJigzRPclEQJXv06L5Ya2HZlthHqrrE0hDHESbChvWs Xc/4ZPAJqfvO9dzLPKuqVfqlFjiFUlcW+xRFNEF3PnRSLrLfqwHV2ycSZEuRsdYLcR YJmBB+Xx7vcnESVGzF2OZaLnmrXpMtFWc4doGhEHD5lyGbqdq2Qu4TsnAY7q50W1WI +eBuwKBGxcdFw== Message-ID: <38c0fbaf-cbb1-4f43-9d45-31ca642d1ed6@kernel.org> Date: Wed, 7 Jan 2026 23:08:29 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v11 3/8] highmem: introduce clear_user_highpages() To: Ankur Arora , linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Cc: akpm@linux-foundation.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, mjguzik@gmail.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, willy@infradead.org, raghavendra.kt@amd.com, chleroy@kernel.org, ioworker0@gmail.com, lizhe.67@bytedance.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com References: <20260107072009.1615991-1-ankur.a.arora@oracle.com> <20260107072009.1615991-4-ankur.a.arora@oracle.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: C9F42A0011 X-Stat-Signature: wi4foz1rbsikh97z1eui8sgcdpe6yb9j X-Rspam-User: X-HE-Tag: 1767823718-513747 X-HE-Meta: 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 u4AxynM1 iZLm9mUGQCgAdMcciI2HVNbSOHazIpbv+HNl6d2PYpnGBtbJkP8+VrWyUrOoVoFdiMAhKXe9uO5rWCBHDKq8LZch6CuQ8rDWnyxDEz9Dye1h2dMZVBdCpSuQfHIscSR//gnF6SSrJGQ7vqP4HMJj41bWvEdBTfzpRDfZZ8rl4FgdaiucW5Tq/6n5NDCbP5cb4xjJw+8TQXwqFO+ypWSRLe1KqiITCxR3zAoAwKgCKPBLWV5E3uZ6yfodewIAyBN5DdE0wv5V4lpqQov1OqJr0STWFUizyhePy9xeCk5qXIZek91aIkGj6mJCEkg== 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 1/7/26 08:20, Ankur Arora wrote: > Define clear_user_highpages() which uses the range clearing primitive, > clear_user_pages(). We can safely use this when CONFIG_HIGHMEM is > disabled and if the architecture does not have clear_user_highpage. > > The first is needed to ensure that contiguous page ranges stay > contiguous which precludes intermediate maps via HIGMEM. > The second, because if the architecture has clear_user_highpage(), > it likely needs flushing magic when clearing the page, magic that > we aren't privy to. > > For both of those cases, just fallback to a loop around > clear_user_highpage(). > > Signed-off-by: Ankur Arora > --- > include/linux/highmem.h | 45 ++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 44 insertions(+), 1 deletion(-) > > diff --git a/include/linux/highmem.h b/include/linux/highmem.h > index 019ab7d8c841..af03db851a1d 100644 > --- a/include/linux/highmem.h > +++ b/include/linux/highmem.h > @@ -251,7 +251,14 @@ static inline void clear_user_pages(void *addr, unsigned long vaddr, > #endif > } > > -/* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */ > +/** > + * clear_user_highpage() - clear a page to be mapped to user space Just a minor comment as I am skimming the patches: I recall kerneldoc does not require the "()" here. But I also recall that it doesn't hurt :) Acked-by: David Hildenbrand (Red Hat) -- Cheers David