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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id ED3DFC982DE for ; Mon, 21 Sep 2026 07:38:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D49786B00C1; Mon, 21 Sep 2026 03:38:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D20CE6B00DF; Mon, 21 Sep 2026 03:38:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C36D26B00E1; Mon, 21 Sep 2026 03:38:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id A0E176B00C1 for ; Mon, 21 Sep 2026 03:38:05 -0400 (EDT) Received: from smtpin18.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 2970D1605ED for ; Mon, 21 Sep 2026 07:38:05 +0000 (UTC) X-FDA: 85236965730.18.231969D Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf30.hostedemail.com (Postfix) with ESMTP id 0B52C80003 for ; Mon, 21 Sep 2026 07:38:02 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=arm.com header.s=foss header.b=l6ko2rle; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf30.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789976283; b=i83OwbS0nYW7cDP9sFLKlspgCIJNROk8prKx1rHrPMz6MmpBT2+WUAoFrz41kDIo/uABHh zKM1OzyNuOQDiNiJcTAjOVXlkiFMX1j1ruCgStl+N/qLKFJRBcbY4T0R5YkCEdGIDN6ujH uq5LSgVrYJVCjBryENDYO3vMHG7OT8E= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=arm.com header.s=foss header.b=l6ko2rle; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf30.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1789976283; 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=qcNAYLYdiq5rOSe15EFUoU8/lzxAYix9CpJvkQBhqoE=; b=DkPNhXiSbcpTA+6jBVg196uq843LWd6KIm7gKBgptCT+7cPuXkQzXsz3G6UJq1nK9jGCZr cwtjEvenyfsoUNhVpYrdOLzpuVaqenHdRSlaWmTQrHBB+aNd9SnhU3XS7FUFSxo9ABq1/9 jkjIowwoH8AL1IW+WtZ5cWS6JK/IeAU= 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 5BB42175A; Mon, 21 Sep 2026 00:37:58 -0700 (PDT) Received: from [10.57.83.12] (unknown [10.57.83.12]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DC0733F86F; Mon, 21 Sep 2026 00:37:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1789976281; bh=nrUjuFhT3s2+v/gwSala4pCbrkVM+7IhP9tittz2bGU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=l6ko2rleUboMNNtjiHiGjklemMccKDrVkhFCxBZ8Sdh5DR4atC+hN8GMVuMwMP5mz 35t8eGH82Xntk2lduJ6VuzvD4tP1J1d2XqoJr0PaLohuTpW2PjZwo3fxqWq6vXhlxV DDTrpBYl7OVsuGeT/5runOY5gbLovztguwJGGIsY= Message-ID: <8d36a988-f6e2-446b-92fd-dc13a4fa691a@arm.com> Date: Mon, 21 Sep 2026 08:37:55 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/6] arm64: use hw_pte_t for fixmap HW PTEs To: "David Hildenbrand (Arm)" , Muhammad Usama Anjum , Catalin Marinas , Will Deacon , Mark Rutland , Ard Biesheuvel , Ilias Apalodimas , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org References: <20260914-pte0_arm-v1-0-bb53b663e396@arm.com> <20260914-pte0_arm-v1-4-bb53b663e396@arm.com> <829523cd-85a4-4f8e-b9f2-f3c1d7ce4fb1@arm.com> <1d1e38d8-cc1a-4a53-80c7-c0ef75a70105@kernel.org> From: Ryan Roberts Content-Language: en-GB In-Reply-To: <1d1e38d8-cc1a-4a53-80c7-c0ef75a70105@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 0B52C80003 X-Stat-Signature: fesmybdp1umakjjopgztkjc97t75d1s7 X-HE-Tag: 1789976282-689779 X-HE-Meta: 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 R72CfyYO CFpRy0chCSq4LGU+SUW0opwuAZhH2ltt8zBdAeqhzPkUoZwOgMObWSo7UCtsQxBfInHPGsvyC3YDqlug/4yRT2qJWFyc5LwgP+MAmgtEtOWPvoHAKKAO/VbyE2bE6DxeHw+qpOnbFSUKcVTj/gSfJ+8EXl6l0YSI3dHD37oB5gpOmywj8AlDAqEsz9W71r8OIbYHKTAng1qla3btI5fnXQk2LT1nIsW0E2eMvapIyzeY81A50sCJUmjbQgIM4TK+l0AkVdBbA12/APJUpEd06PptRJFYxnOrMgiyXkrfF0R+24t2hJ4xiBIYRIikk/LWVTFxiSwlmjWDm9pOnG0Wch42Ouuyw3+cF/WUuAN16ADP8qMqExJ/2oWzMGkvkjDLejDiv4JI4k2QGVxnEa3LwJPXCG7eRayptm3qX Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 18/09/2026 21:00, David Hildenbrand (Arm) wrote: > On 9/18/26 18:03, Ryan Roberts wrote: >> On 14/09/2026 14:51, Muhammad Usama Anjum wrote: >>> fixmap_pte() returns a pointer into bm_pte, and early_fixmap_init_pte() >>> installs those arrays as page tables. Their elements are therefore >>> HW PTEs. >>> >>> Change the element type of bm_pte to hw_pte_t so it matches the HW PTE >>> pointers returned and passed to the accessors. This is needed before >>> ARCH_HAS_HW_PTE_T makes HW PTEs and SW PTE values distinct types; the >>> array dimensions and placement are unchanged. >>> >>> Signed-off-by: Muhammad Usama Anjum >>> --- >>> arch/arm64/mm/fixmap.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/arch/arm64/mm/fixmap.c b/arch/arm64/mm/fixmap.c >>> index 237a9136bc73b..709a97fe327d8 100644 >>> --- a/arch/arm64/mm/fixmap.c >>> +++ b/arch/arm64/mm/fixmap.c >>> @@ -31,7 +31,7 @@ static_assert(NR_BM_PMD_TABLES == 1); >>> >>> #define BM_PTE_TABLE_IDX(addr) __BM_TABLE_IDX(addr, PMD_SHIFT) >>> >>> -static pte_t bm_pte[NR_BM_PTE_TABLES][PTRS_PER_PTE] __bss_pgtbl; >>> +static hw_pte_t bm_pte[NR_BM_PTE_TABLES][PTRS_PER_PTE] __bss_pgtbl; >> >> I think in my original proposal it was impossible to have a hw_pte value; only a >> hw_pte pointer was possible. Being able to create hw_pte values means that it is >> possible that a hw_pte_t pointer is not actually pointing to an entry in a HW >> pgtable. The main motivation for this is that we want to dereference neighbours >> of a hw pte based on it's pointer and be confident that it is safe. I think this >> removes some of the safety. > > If you follow some of the related discussions on the core-mm series, there is a > path forward to go further into that direction. OK, as long as we have a path to the "full" solution if we ever need it, then sounds good to me. > > People instantiating a hw_pte_t on the stack are not really a concern right now. >