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 61F29C54F52 for ; Wed, 29 Jul 2026 13:58:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 38B556B00A9; Wed, 29 Jul 2026 09:57:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 36AB06B00AA; Wed, 29 Jul 2026 09:57:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2045F6B00AB; Wed, 29 Jul 2026 09:57:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id ECEB36B00A9 for ; Wed, 29 Jul 2026 09:57:58 -0400 (EDT) Received: from smtpin10.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id E18631206A7 for ; Wed, 29 Jul 2026 12:42:44 +0000 (UTC) X-FDA: 85041778248.10.0F2FF89 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf02.hostedemail.com (Postfix) with ESMTP id 437C680006 for ; Wed, 29 Jul 2026 12:42:43 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=OIiVNrud; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1785328963; 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=CCfnfjBFYExAnxJTD/rzMs4G+JVWk8LnuYF1LstcYDw=; b=voRpqMs0RiVLromeLLMN1I+nVoKLcKaqcE8TRuriXmsssY4RrhYwXtWatPS7jVkK8FpHCy /MFSrFojgfATIIj1CaE0Jd3BiA2gYL9ankwzoqmT18hszY+AQyxo07ZjZLftzZx3uGRLFK B3ZZBrIGba7DAKSBCpNZ1XQQzDpGlt8= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1785328963; b=4G87AQx66R6LU/vuzfxJYQ3Jgubly9Iba+iRGiToQDGx6fG8zEjUcjz8nog9Kftw92ptDL P6S6gX8KYe8PM6ChXfXNZ0YFQJfuc7SBcP1rn1UynGzmQ6sjECEEc0Lyc53MlCRZQjDh7Z 7/VqSRdZ40SfDVN/eRCAGKPszd4uyOo= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=OIiVNrud; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id B98626004E; Wed, 29 Jul 2026 12:42:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4D1321F000E9; Wed, 29 Jul 2026 12:42:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785328962; bh=CCfnfjBFYExAnxJTD/rzMs4G+JVWk8LnuYF1LstcYDw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=OIiVNrudGYMgEdVIx0kkjz41K/abfMmWQCuVMoltvKL88ry5vvzeu9fzcY/9OXDWp urmM5jTj5uYEwxtowv6dnJlwSS9PTo7quWtNi7gHj3ZqfWleJMlYHWWtwoq0IDEkky 8P8JnLCx+cJFeHdNFsas608FWlQT7bVkC2bwM046FAmQ7zDEHB0zW1hDtHOw8f8bql 4k70NlZODBKCZTfjYFNVdqOJ/v1f/eicr7a9D82muWKPn8AlDCyXeFCuwaSWyiZ0iA 7EW64naZjqP6zUdWAdVwIEaL++olcUVsOGEeMV8mWUj+uyYo7qTGP16v8aSA/cUEkI 1GtsvDfHUTVwQ== Message-ID: <5abb6bbb-973e-41e7-820c-057e85edeb95@kernel.org> Date: Wed, 29 Jul 2026 14:42:30 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 09/11] misc/sgi-gru: use ptep_get() for page-table reads To: Pedro Falcato , Muhammad Usama Anjum Cc: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Dimitri Sivanich , Arnd Bergmann , Greg Kroah-Hartman , "James E.J. Bottomley" , Helge Deller , Juergen Gross , Stefano Stabellini , Muchun Song , Oscar Salvador , Andrew Morton , "Liam R. Howlett" , Lorenzo Stoakes , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Andrey Ryabinin , Pasha Tatashin , Chris Li , Kairui Song , Uladzislau Rezki , Steven Rostedt , Masami Hiramatsu , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , SJ Park , "Matthew Wilcox (Oracle)" , Jan Kara , Jason Gunthorpe , Leon Romanovsky , Miaohe Lin , Dennis Zhou , Tejun Heo , Christoph Lameter , Mike Rapoport , Johannes Weiner , ziy@nvidia.com, agordeev@linux.ibm.com, ryan.roberts@arm.com, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-parisc@vger.kernel.org, xen-devel@lists.xenproject.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, kasan-dev@googlegroups.com, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, damon@lists.linux.dev References: <20260727164715.2866609-1-usama.anjum@arm.com> <20260727164715.2866609-10-usama.anjum@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 X-Rspamd-Queue-Id: 437C680006 X-Stat-Signature: 1b58sxadugpihr48qqpgfh1zoq8rcbxz X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1785328963-98920 X-HE-Meta: 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 bh/Ouk7f DFN99o03Kb5JRRb8UiR5Q8vnOrde3BZ3X0yNJRzqmhuzigMxdugoVh9AtOwWah4GkYj6eEoEHc+p7KhUZKXswHmPco/6d9mx5ZenNk50/D9ZGWqOOQ+BjBxkfSO+I0zgquR5ONrc3nkEG5BTHlbaQh+7ienINSXzSKbcyMLd3l7PidVSS0hgQYg8DkE8OajO/XrPJ9xSq5zvMh32VnqaAQbidDFZZXbpoOX7r3JOYAezr4/w8/61fAvVUUSlnNMDpzXdlE0IuaWi7ZQT3DKsqeNGgW6PF0EidRQVqKBu1dEYn9Zpnhc78aTVfGf1sHzfUSfvpWRrom30Hv8qkq3RnroFO7oAlzUHnwCuPOqtM4SRYlIxX0sKegt2jqFRKW0hngumFlfyO0S2/gKn+uVABdpd3+QtjYvKZ0XjLsYBFtXK3BYR701eyz8J80Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/29/26 14:36, Pedro Falcato wrote: > On Mon, Jul 27, 2026 at 05:47:00PM +0100, Muhammad Usama Anjum wrote: >> A leaf PMD is being read through ptep_get() by treating the PMD address >> as PTE-sized table storage. ptep_get() now accepts hw_pte_t *, so update >> the cast accordingly. >> >> pte_offset_kernel() also returns hw_pte_t *. Get pte_t value by calling >> ptep_get(). >> >> Signed-off-by: Muhammad Usama Anjum >> --- >> drivers/misc/sgi-gru/grufault.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c >> index 3557d78ee47a2..ff89d34ad2aa4 100644 >> --- a/drivers/misc/sgi-gru/grufault.c >> +++ b/drivers/misc/sgi-gru/grufault.c >> @@ -228,10 +228,10 @@ static int atomic_pte_lookup(struct vm_area_struct *vma, unsigned long vaddr, >> goto err; >> #ifdef CONFIG_X86_64 >> if (unlikely(pmd_leaf(*pmdp))) >> - pte = ptep_get((pte_t *)pmdp); >> + pte = ptep_get((hw_pte_t *)pmdp); >> else >> #endif >> - pte = *pte_offset_kernel(pmdp, vaddr); >> + pte = ptep_get(pte_offset_kernel(pmdp, vaddr)); >> >> if (unlikely(!pte_present(pte) || >> (write && (!pte_write(pte) || !pte_dirty(pte))))) > > This code is super, super broken. Can we remove this ASAP? For starters, > we're using is_vm_hugetlb_page() to detect page shift, the code does not > grab refs on the pages, uses pte_offset_kernel() on user page tables, > does not handle PUD-level hugepages, does not handle PMD-level hugepages on !x86_64, > does not hold page table locks nor check for pte table retraction, etc > > I don't think I need to go on. > Heh, when Usama first showed me an early diffstat I was like "what the hell are drivers doing with page tables here, they shouldn't be doing that". atomic_pte_lookup documents: "Only supports Intel large pages (2MB only) on x86_64. ZZZ - hugepage support is incomplete" What is this crap? :) -- Cheers, David