From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CB1DDC55822 for ; Tue, 4 Aug 2026 13:09:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:References:Cc:To:Subject:From:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=4f7ucuIUW8vF4hICwF+LuP1Ke4k5i/LOY8wkqoppgQU=; b=rlEz+vp7Z7te7doBk+pucz2gZ6 JOO9L4CbfgSfyJpPG+xHZvVLykI3wGEDkpRZxbn/np/ByHeHfXIKsW4Qrx42UukA3Ek9pLrQIurKy auDl5yoJoF2RFLf2iwBAdOtavmaKJ7VTr2GDNV5BKWs0RUnRvbkKycT24nK8yBSPvfg6xoFTpjgo5 m329Ioerg6V1SOk6Ht4Pn0aETJhLvLXKcB3zmUB2g46B+DyZXf3VgjcAydUdyiTQIn2lfkcgJHSYg BpX3vaxlZp/fNrsVvmsQLWOVaC9CF8ARhX511GENXL5kqi3TD/v8wGWOOhasroNxiuz3g4op2OW1F n7qu1IMg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wrEta-00000001t9L-1TSy; Tue, 04 Aug 2026 13:09:26 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wrEtZ-00000001t98-202N for linux-arm-kernel@lists.infradead.org; Tue, 04 Aug 2026 13:09:25 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id C209E60A59; Tue, 4 Aug 2026 13:09:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 61BCF1F000E9; Tue, 4 Aug 2026 13:09:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785848964; bh=4f7ucuIUW8vF4hICwF+LuP1Ke4k5i/LOY8wkqoppgQU=; h=Date:From:Subject:To:Cc:References:In-Reply-To; b=Ui7t6UYnjDGA7jUXdMOZJ6Axzrun5isfzKVm2Uxl2vfraDeFP2914FnkkgGhu02mt voOMjZW+YQ46kAl40nY5yZAVMVTwc2qmAKmCz9LQhk5ulRqhzZ/m3BmyZQAM9NVgx8 FwOD9Y8T/fvcC5vlvAad/UEgX4uXdJMGHYQlatXXVZVZd+jSgiNaUDo3eXIDHUpHPb H9f3aviudsPqRTHHXbL4Vk5hI08JKwkf42AE7BMOT0rqjFGPcbbnzBwf1XrdOxPL93 HRXzP9YkSZKmWwWsTd+SDFdFB4YbPaM8pEuJ0zHw4olpd2r+ILT02xSPpdClMWKtk7 45CLGnbTDgBTw== Message-ID: <6bd4f498-6699-4d54-a43a-57c954bff958@kernel.org> Date: Tue, 4 Aug 2026 15:09:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: "Christophe Leroy (CS GROUP)" Subject: Re: [PATCH v2 3/6] mm/powerpc/8xx: constify ptep_get() argument To: "Lorenzo Stoakes (ARM)" Cc: Pedro Falcato , David Hildenbrand , Andrew Morton , Catalin Marinas , Will Deacon , "James E.J. Bottomley" , Helge Deller , Madhavan Srinivasan , Michael Ellerman , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kevin Brodsky , Muhammad Usama Anjum , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org References: <20260803164400.531199-1-pfalcato@suse.de> <20260803164400.531199-4-pfalcato@suse.de> Content-Language: fr-FR In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Le 04/08/2026 à 14:59, Lorenzo Stoakes (ARM) a écrit : > On Tue, Aug 04, 2026 at 02:50:19PM +0200, Christophe Leroy (CS GROUP) wrote: >> Hi Lorenzo, >> >> Le 04/08/2026 à 13:13, Lorenzo Stoakes (ARM) a écrit : >>> On Mon, Aug 03, 2026 at 05:43:57PM +0100, Pedro Falcato wrote: >>>> There is no need for write access to the PTE. >>>> >>>> Signed-off-by: Pedro Falcato >>> >>> With below addressed LGTM so: >>> >>> Reviewed-by: Lorenzo Stoakes (ARM) >>> >>>> --- >>>> arch/powerpc/include/asm/nohash/32/pte-8xx.h | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/arch/powerpc/include/asm/nohash/32/pte-8xx.h b/arch/powerpc/include/asm/nohash/32/pte-8xx.h >>>> index e2ea8ba9f8ca..f2bab31040c7 100644 >>>> --- a/arch/powerpc/include/asm/nohash/32/pte-8xx.h >>>> +++ b/arch/powerpc/include/asm/nohash/32/pte-8xx.h >>>> @@ -226,7 +226,7 @@ static inline pte_basic_t pte_update(struct mm_struct *mm, unsigned long addr, p >>>> >>>> #ifdef CONFIG_PPC_16K_PAGES >>>> #define ptep_get ptep_get >>>> -static inline pte_t ptep_get(pte_t *ptep) >>>> +static inline pte_t ptep_get(const pte_t *ptep) >>>> { >>>> pte_basic_t val = READ_ONCE(ptep->pte); >>>> pte_t pte = {val, val, val, val}; >>> >>> Worth making these const too (that {val, val, val, val} horrifies me btw :)? >> >> Any suggestion welcome. > > I'm being super nitty, all I mean is: > > - pte_basic_t val = READ_ONCE(ptep->pte); > - pte_t pte = {val, val, val, val}; > + const pte_basic_t val = READ_ONCE(ptep->pte); > + const pte_t pte = {val, val, val, val}; > > :) I'm fine with that, I was reacting on the "horrifying". > >> >> powerpc 8xx page table is independant on page size. When you use 16k pages, >> depending on the address you hit the page for the first time, the HW assist >> page table walk will fetch one of four 4k cells in page table that need to >> be identical as they all four define the same 16k page. Not sure I'm clear. > > No that's clear, thanks! > > (I say 'horrifying' because I am looking into RCU page table freeing which this > may complicate, though perhaps not in practice, to be continued :) A few more details here if needed: 55c8fc3f4930 ("powerpc/8xx: reintroduce 16K pages with HW assistance") Christophe