From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0F0CA42980A; Fri, 27 Feb 2026 20:55:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772225750; cv=none; b=LUV8sKviUmuQ4DIOVPeqrM1ZrxHSNk07w6ESq7oEZge9BC0DED1M0YCjjoeQGmRNLb4g5/+ZG10Vm5YeA5mzvC7M2DB/Li2cJuORnqflvg0l6GuW5PrwRRzhxYQpcHwKMCaYrXb/rtNbRZ0gmFB2KgHrbX1o99KFrKmSbXTDC0Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772225750; c=relaxed/simple; bh=RcLgvWL4EWw0I9N2SCEA7PiWOjdOzlqk9NEbntyOnoc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=dIprzewAbV8jSPA4p1tTIxLL+8oPKMWGtqeCxFQatlGwZbyNGRaExm7lHVFw1Ip3j/Q3OmZpRLZySTAmqMgjt1TylYO8NUYZgQc0nT15VkSMBv/drwe8WDl3s4rAFk4Y6hJhTAZAQFvJb0SQN98KDT23ftxE+9O23DPA0ieJOxM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ec5EmqEi; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ec5EmqEi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 71F6CC2BC9E; Fri, 27 Feb 2026 20:55:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772225749; bh=RcLgvWL4EWw0I9N2SCEA7PiWOjdOzlqk9NEbntyOnoc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ec5EmqEi8Tuh9mTsaLR2NyeFZLdI9fBDmozhfEZ4YpGe2RFN2Iyl61G2P5gtlxp3y VTn8OXE3D/Lm/yvrWsIKkTSDETCKnR9MU1VlqG/AbVWvH6JssNSLT2ZuNF2lvdzJJl Ony94uN9+P6ItRlZD0y0VZZMFuLOUSip3ayAhmQXfc6+c2MPRqsMR5nJCUSseJjHCw s1dpzIhmQJsCsqbsPU/z4cgaHimb+rB72zF7FBAVtCWy153opI7bU7Xa16mHsMTG4Z Xxunnz2J25EbvKNvep0Ylb+cyXxLf8CUUmfUw1r3cAq+/A+4ghhKTzGg1e7lBk2fEM 38QyluppoKojw== Message-ID: <74f0b99f-5184-448f-a5b0-fb8c827028ee@kernel.org> Date: Fri, 27 Feb 2026 21:55:45 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] perf/events: Replace READ_ONCE() with standard pgtable accessors To: Anshuman Khandual , linux-mm@kvack.org Cc: Andrew Morton , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260227062744.2215491-1-anshuman.khandual@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/27/26 07:27, Anshuman Khandual wrote: > Replace raw READ_ONCE() dereferences of pgtable entries with corresponding > standard page table accessors pxdp_get() in perf_get_pgtable_size(). These > accessors default to READ_ONCE() on platforms that don't override them. So > there is no functional change on such platforms. > > However arm64 platform is being extended to support 128 bit page tables via > a new architecture feature i.e FEAT_D128 in which case READ_ONCE() will not > provide required single copy atomic access for 128 bit page table entries. > Although pxdp_get() accessors can later be overridden on arm64 platform to > extend required single copy atomicity support on 128 bit entries. > > Cc: Andrew Morton > Cc: David Hildenbrand > Cc: Peter Zijlstra > Cc: Ingo Molnar > Cc: Arnaldo Carvalho de Melo > Cc: Namhyung Kim > Cc: linux-perf-users@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Acked-by: Peter Zijlstra (Intel) > Signed-off-by: Anshuman Khandual > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David