From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E389D305E28; Fri, 12 Jun 2026 11:14:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781262859; cv=none; b=e9w/qSTYE8bpW1CLzTN88M/RLHgo8w1FZ5qmRNY++LQlyZwVi29qvWjTV6utVQF6EKX23Q3B/z+rcvHCwzHALnrjxnvX6IHYVF+HgkI9boZDwLPaZnSWEM49hcIPM+HMjHPDOEP2+0P3gjjKeiGbnefpfkzAWtRRFwDdwYNejaA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781262859; c=relaxed/simple; bh=J+9LWesfez5uYUFNLOKtrhGdIhGy9L/aeiQe+dudL+c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=riep10v2syTKMngWxgrz4hY/cp6FCX55o8gzOugVzufLU1GrnJBa/QMA7rr3sa/LM0U5vlPpxMwsViwRJLur4Vw17IzNbC7Rd5k6haThK3oag1uBc3QavtWCOCYzFERjgj5hb4jSdRo28UmuRCBg921Hf70cntsAVV4mZuZQ7dY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=n+h/dgKk; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="n+h/dgKk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1E07F1F000E9; Fri, 12 Jun 2026 11:14:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781262856; bh=dP7e3JEtOPtC6CVM3VUIPHIKZe0OVbKMvYxoe2ZHRtY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=n+h/dgKkcBlo/dGQjj1ub3s9bjOa0M2la6urtdxD0te37aVSmCofz0hyWaifbPk20 mS8IHjwYOyPvqcGFKrUnRefPCHeAQFySphnvGxKPQLj4KzCYeGzPYq+BCR3cj4vCA6 viFy8LB1SAvbHyu/PXVcxGxXFGzLV4lIpsWxWktEtHo8/sTXJB2/0K71s+fSdPIhB3 nX9RflZcxKhiUeUSMoVeyVE4jZT8zOB7eNZFF7cKPGRJ0xB0z3EYGyPa61BN7W9knN 4GxyBMUDop4P3Sk7/axoqTQA3bJ8OeJqcVc3VI47d8arWIzRyxwP4RvDi6JVUKjcj3 qAM2UyRRNtqIg== Message-ID: <3603c37b-95b1-4d29-ab6f-fa3360dc17db@kernel.org> Date: Fri, 12 Jun 2026 13:14:12 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC V2 0/3] lib/vsprintf: Add support for pgtable entries To: Matthew Wilcox , Andy Shevchenko Cc: Anshuman Khandual , linux-mm@kvack.org, Rasmus Villemoes , Sergey Senozhatsky , Petr Mladek , Steven Rostedt , Jonathan Corbet , Andrew Morton , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org References: <20260610043545.3725735-1-anshuman.khandual@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 On 6/11/26 21:37, Matthew Wilcox wrote: > On Thu, Jun 11, 2026 at 10:33:35PM +0300, Andy Shevchenko wrote: >> On Thu, Jun 11, 2026 at 08:15:57PM +0100, Matthew Wilcox wrote: >>> >>> You didn't address my objection here: >>> >>> https://lore.kernel.org/linux-mm/aFQP8LzVMctf6XH5@casper.infradead.org/ >>> >>> ie there is now no typechecking possible. So you've made it more >>> dangerous. I reiterate my NACK to the concept, not to the implementation. >> >> But this is more of a global question, how do we check the validity of >> the parameters of pointer extensions in the kernel? Does anybody go to >> commit into GCC plugin or so for this job? > > I agree that it's a global question that it would be great for somebody > to answer. But it's specifically a problem for this patchset because: > > - It's really easy to get confused about which page table level you're > working on. And hugetlbfs deliberately increases that confusion. Yeah ... so far I was assuming that for hugetlb, all relevant entries (what we call a PTE although it isn't ....) would have to be the same size. I mean, at least in the callers they are the same size (pte_t) > - Different levels of the page tables actually do have different sizes > on some architectures, so if you think you're looking at a pointer to a > 64-bit quantity when it's really a pointer to a 32-bit quantity, things > Will Go Wrong (or vice-versa. And some architctures are big-endian) I see your point with the pass-by-pointer. > - But on x86-64, Everything Is Fine because all levels of the page table > are basically identical, so you'll never notice there's a problem. I assume on most architectures. Let's see if we can stop printing that information completely, so we can avoid messing with this at all. -- Cheers, David