From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 78ABC3BB9E5; Wed, 8 Apr 2026 10:58:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775645937; cv=none; b=aaSimOBORG8LUwV3zsqsjvOVhmwe2+deXmDXvDWmwZDiSPaS29EuGUhmodgXVPeNmXAM8BqxgvZgG0PudvSKbHDKMCGuBHmVWNOsOlT+ARxz+zMAgaYgwxCERYHLsx8bMvFPvOe2VPVzT2mNxW4CuLELF9vnYhItl12QNE4dJHY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775645937; c=relaxed/simple; bh=rvCB0mtFCTChcch/FM64LYIf0vr0IZ0WwJBCN05cnQg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=bGK3zsglDxRo4s7lzcb7gqO2B0jBeUrGuINZtSrKa76IAW0Hm6vZVQvWK03UpjUrSkx3HzcPB2nPHW/9Zcb0SB9quvTaOUFcD8DJ5rGXlnqG+MTmUiendzmcvV+Rl3fWPZ3QqODLZtaPKbEtXHo5A50frWxc5/JUF/uamIdw0u8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=ZSPo+kwj; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="ZSPo+kwj" 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 0A7303161; Wed, 8 Apr 2026 03:58:49 -0700 (PDT) Received: from [10.163.180.198] (unknown [10.163.180.198]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F23E23F632; Wed, 8 Apr 2026 03:58:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1775645934; bh=rvCB0mtFCTChcch/FM64LYIf0vr0IZ0WwJBCN05cnQg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ZSPo+kwjikI+iRW4adeq1Vx/UxwAGFrfNhig45c90krMMeJUQpomGNau9pTkioJg3 mzGBxrK+v+q1P5KG9fHhUFQbVCAaYZnRtbR6gS4JFEchs1JRDpB3ykj9MtEMsAjDi7 VnrqcD848OeDpenFRsURVEewmf1UU4/17K4SfAjM= Message-ID: Date: Wed, 8 Apr 2026 16:28:48 +0530 Precedence: bulk X-Mailing-List: linux-perf-users@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: Peter Zijlstra , "David Hildenbrand (Arm)" Cc: linux-mm@kvack.org, Andrew Morton , 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> <1267a6c0-f8e7-4708-96da-4d131b5c6069@arm.com> <20260407071820.GA3738010@noisy.programming.kicks-ass.net> Content-Language: en-US From: Anshuman Khandual In-Reply-To: <20260407071820.GA3738010@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 07/04/26 12:48 PM, Peter Zijlstra wrote: > On Tue, Apr 07, 2026 at 08:48:22AM +0200, David Hildenbrand (Arm) wrote: >> On 4/7/26 05:28, Anshuman Khandual wrote: >>> >>> >>> On 27/02/26 11:57 AM, 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 >>>> --- >>>> This patch applies both on v7.0-rc1 and mm-unstable. >>>> >>>> Part of the D128 series but independent. Hence could be considered on its own. >>>> >>>> https://lore.kernel.org/all/20260224051153.3150613-5-anshuman.khandual@arm.com/ >>>> >>>> Collected Peter's tag from an off list conversation. >>> >>> Gentle ping. >>> >>> Still don't see this patch in latest next-20260406. Hence just >>> wondering which tree and branch this patch is being picked up ? >> >> It's a trivial change and the last generic code change required for you >> arm64 D128 change, right? >> >> I would assume this to go through the tip tree, but if Peter agrees we >> could route this (mm) patch through the MM tree. > > Right, I thought this was part of a larger series and figured it would > ride along with whatever other patches. > > If you still want me to pick this up, I can, just state clearly where > this ought to go. It would be great if you could pick this up. Thanks !