From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0AA1F36F8F3 for ; Tue, 14 Jul 2026 10:26:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.130 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784024797; cv=none; b=PHRhpQF+UEEe6arZ5q6OJi28S4cgOyqolylrQGnSsXptwSfy19YRAC3RdpZUfvy7QP+9UaYXV3/BEaRGPLPQ6znkrvEzPWwr00qu+gBR4XqOwSik8Xtj1YyrMNtTLuzxEIfeH+H7u5ARCEbUyughGI6AS3d5t7Do92aG0bBNXfo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784024797; c=relaxed/simple; bh=wRvxYrU0Db74kgKIg4MAkH8AJ48uHcgqYHktBr4Iftk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=D6kUpSPRnR7P54P6/j39lqHWBix+RCcCGfUhruleaSUCYziB6xCtyEhaB75gTQg7yvdwW4gx1Vdj9x1pxh+3ATTCmI/I/oIUSVj+ERr15VoWvliudXOsv5rELyDRj77ktRVNd1ktoJ2aRtkjNfyqMv6geHkAe3V+63IF8nXV3CA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de; spf=pass smtp.mailfrom=suse.de; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b=X1UcKjUP; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b=DPgDPUNa; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b=X1UcKjUP; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b=DPgDPUNa; arc=none smtp.client-ip=195.135.223.130 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b="X1UcKjUP"; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b="DPgDPUNa"; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b="X1UcKjUP"; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b="DPgDPUNa" Received: from imap1.dmz-prg2.suse.org (unknown [10.150.64.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 134CB75D55; Tue, 14 Jul 2026 10:26:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1784024793; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=khB/to3aOpUTgGTf59zKb1ob5wdV92G9QJtQXjDAoS4=; b=X1UcKjUPwFCkcvM34/QaEi0GeBdnyXah3hmHi1D8Poz47UB712qXIXRaJG6edsNfbG2ZA+ z5cB65T9O/OYv5qY43ugJDHwVaTgllfBIZ9UaWwkNvt07EqCc4MfDsXlOrzcTa1ljoJsh8 ZREca7S8uqp/stNOGwDBdmvskz1XeX0= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1784024793; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=khB/to3aOpUTgGTf59zKb1ob5wdV92G9QJtQXjDAoS4=; b=DPgDPUNaL/Uj8oEf2qMTyo3J81KosNcpxLKOMxymAIDnO1BMA1vluTZ6/clWzrYO9GdgP4 w321jUwSCwkNL+AA== Authentication-Results: smtp-out1.suse.de; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1784024793; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=khB/to3aOpUTgGTf59zKb1ob5wdV92G9QJtQXjDAoS4=; b=X1UcKjUPwFCkcvM34/QaEi0GeBdnyXah3hmHi1D8Poz47UB712qXIXRaJG6edsNfbG2ZA+ z5cB65T9O/OYv5qY43ugJDHwVaTgllfBIZ9UaWwkNvt07EqCc4MfDsXlOrzcTa1ljoJsh8 ZREca7S8uqp/stNOGwDBdmvskz1XeX0= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1784024793; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=khB/to3aOpUTgGTf59zKb1ob5wdV92G9QJtQXjDAoS4=; b=DPgDPUNaL/Uj8oEf2qMTyo3J81KosNcpxLKOMxymAIDnO1BMA1vluTZ6/clWzrYO9GdgP4 w321jUwSCwkNL+AA== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 0B7FB779AE; Tue, 14 Jul 2026 10:26:26 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id PH4iO9IOVmoNJQAAD6G6ig (envelope-from ); Tue, 14 Jul 2026 10:26:26 +0000 Date: Tue, 14 Jul 2026 11:26:20 +0100 From: Pedro Falcato To: Yeoreum Yun Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-arch@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, x86@kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com, linux-csky@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org, david@kernel.org, linux@armlinux.org.uk, akpm@linux-foundation.org, ankur.a.arora@oracle.com, rppt@kernel.org, linmag7@gmail.com, chleroy@kernel.org, klarasmodin@gmail.com, chenhuacai@kernel.org, kernel@xen0n.name, kas@kernel.org, zhangtianyang@loongson.cn, wangyuli@aosc.io, tsbogend@alpha.franken.de, ljs@kernel.org, jgg@ziepe.ca, catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de, ryan.roberts@arm.com, pasha.tatashin@soleen.com, rmclure@linux.ibm.com, baolin.wang@linux.alibaba.com, tj@kernel.org, kevin.brodsky@arm.com, anup@brainfault.org, atish.patra@linux.dev, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, hannes@cmpxchg.org, mhocko@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, kasong@tencent.com, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, ryabinin.a.a@gmail.com, glider@google.com, andreyknvl@gmail.com, dvyukov@google.com, vincenzo.frascino@arm.com, anshuman.khandual@arm.com, yang@os.amperecomputing.com, chaitanyas.prakash@arm.com, ardb@kernel.org, guoren@kernel.org, yang.li85200@gmail.com, viro@zeniv.linux.org.uk, dinguyen@kernel.org, schuster.simon@siemens-energy.com, wangruikang@iscas.ac.cn, junhui.liu@pigmoral.tech, muchun.song@linux.dev, vishal.moola@gmail.com, namcao@linutronix.de, pavel@kernel.org, djbw@kernel.org, yu-cheng.yu@intel.com, baolu.lu@linux.intel.com, Jonathan.Cameron@huawei.com, coxu@redhat.com, andreas@gaisler.com, liam@infradead.org, vbabka@kernel.org, surenb@google.com, mhocko@suse.com, geert@linux-m68k.org, shorne@gmail.com, jonas@southpole.se, stefan.kristiansson@saunalahti.fi Subject: Re: [RFC PATCH 02/34] ARM: mm: make 2-level pgd_t a scalar Message-ID: References: <20260713135614.1618183-1-yeoreum.yun@arm.com> <20260713135614.1618183-3-yeoreum.yun@arm.com> Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260713135614.1618183-3-yeoreum.yun@arm.com> X-Spam-Flag: NO X-Spamd-Result: default: False [-2.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FUZZY_RATELIMITED(0.00)[rspamd.com]; MISSING_XM_UA(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; TAGGED_RCPT(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[lists.infradead.org,vger.kernel.org,lists.linux.dev,kernel.org,kvack.org,googlegroups.com,lists.linux-m68k.org,armlinux.org.uk,linux-foundation.org,oracle.com,gmail.com,xen0n.name,loongson.cn,aosc.io,alpha.franken.de,ziepe.ca,arm.com,arndb.de,soleen.com,linux.ibm.com,linux.alibaba.com,brainfault.org,linux.dev,dabbelt.com,eecs.berkeley.edu,ghiti.fr,linux.intel.com,infradead.org,redhat.com,alien8.de,zytor.com,cmpxchg.org,tencent.com,google.com,os.amperecomputing.com,zeniv.linux.org.uk,siemens-energy.com,iscas.ac.cn,pigmoral.tech,linutronix.de,intel.com,huawei.com,gaisler.com,suse.com,linux-m68k.org,southpole.se,saunalahti.fi]; R_RATELIMIT(0.00)[to_ip_from(RLdozb9qxkmspn1ke6sq1inr93)]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_SOME(0.00)[]; RCPT_COUNT_GT_50(0.00)[95]; DBL_BLOCKED_OPENRESOLVER(0.00)[arm.com:email,imap1.dmz-prg2.suse.org:helo] X-Spam-Level: X-Spam-Score: -2.30 On Mon, Jul 13, 2026 at 02:55:41PM +0100, Yeoreum Yun wrote: > From: "David Hildenbrand (Arm)" > > We don't want pgd_t to be an array, as it prohibits returning it from a > function, like pgdp_get(). > > So let's just use an u64, and extract the right 32bit value in > pgd_val(). > > Leave the STRICT_MM_TYPECHECKS case alone for now. I have to ask: is there a good reason for the STRICT_MM_TYPECHECKS ifdef? I see the compiler has an awkward time returning a u64 struct (see https://godbolt.org/z/qejbv6j9a), but if this doesn't work maybe we should get rid of the STRICT_MM_TYPECHECKS stuff? I seriously doubt anyone is purposefully toggling it on for testing from time to time. If STRICT_MM_TYPEDEFS's worse codegen doesn't matter then maybe we should permanently toggle it on. > > As an alternative, we could use the STRICT_MM_TYPECHECKS approach here > as well, but using an u64 looks conceptually cleaner, even though > pgd_val() gets a bit more involved. > > Signed-off-by: David Hildenbrand (Arm) > Signed-off-by: Yeoreum Yun > --- > arch/arm/include/asm/pgtable-2level-types.h | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/arch/arm/include/asm/pgtable-2level-types.h b/arch/arm/include/asm/pgtable-2level-types.h > index 650e793f41429..02052cef9437a 100644 > --- a/arch/arm/include/asm/pgtable-2level-types.h > +++ b/arch/arm/include/asm/pgtable-2level-types.h > @@ -25,7 +25,7 @@ typedef struct { pteval_t pgprot; } pgprot_t; > > #define pte_val(x) ((x).pte) > #define pmd_val(x) ((x).pmd) > -#define pgd_val(x) ((x).pgd[0]) > +#define pgd_val(x) ((x).pgd[0]) > #define pgprot_val(x) ((x).pgprot) > > #define __pte(x) ((pte_t) { (x) } ) > @@ -36,14 +36,21 @@ typedef struct { pteval_t pgprot; } pgprot_t; > /* > * .. while these make it easier on the compiler > */ > +typedef u64 pgdval_t; > + > typedef pteval_t pte_t; > typedef pmdval_t pmd_t; > -typedef pmdval_t pgd_t[2]; > +typedef pgdval_t pgd_t; > typedef pteval_t pgprot_t; > > #define pte_val(x) (x) > #define pmd_val(x) (x) > -#define pgd_val(x) ((x)[0]) > + > +static inline pmdval_t pgd_val(pgd_t pgd) > +{ > + return (*(pmdval_t (*)[2])&pgd)[0]; Ugh. This isn't correct C code. It only works because the kernel passes -fno-strict-aliasing. I would recommend either forcing a struct here, or using a u64 with bitmasks/shifts. -- Pedro