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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 86BB8C48260 for ; Tue, 13 Feb 2024 14:22:16 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4TZ3S71F5Tz3vYH for ; Wed, 14 Feb 2024 01:22:15 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=arm.com (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=ryan.roberts@arm.com; receiver=lists.ozlabs.org) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lists.ozlabs.org (Postfix) with ESMTP id 4TZ3Rb3Gqnz30f8 for ; Wed, 14 Feb 2024 01:21:44 +1100 (AEDT) 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 355E0DA7; Tue, 13 Feb 2024 06:21:53 -0800 (PST) Received: from [10.1.36.184] (XHFQ2J9959.cambridge.arm.com [10.1.36.184]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5BF583F762; Tue, 13 Feb 2024 06:21:08 -0800 (PST) Message-ID: Date: Tue, 13 Feb 2024 14:21:07 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 19/25] arm64/mm: Wire up PTE_CONT for user mappings Content-Language: en-GB To: Ard Biesheuvel , David Hildenbrand References: <20240202080756.1453939-1-ryan.roberts@arm.com> <20240202080756.1453939-20-ryan.roberts@arm.com> <64395ae4-3a7d-45dd-8f1d-ea6b232829c5@arm.com> <41499621-482f-455b-9f68-b43ea8052557@redhat.com> <1d302d7a-50ab-4ab4-b049-75ed4a71a87d@arm.com> <99e2a92c-f2a2-4e1e-8ce2-08caae2cb7e4@redhat.com> <64b872bd-4b12-4dbd-b043-1ad11aeaa19a@redhat.com> <3de2130b-9f0f-4a11-ac06-7bf814de641c@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Kefeng Wang , x86@kernel.org, Catalin Marinas , Yang Shi , Dave Hansen , linux-mm@kvack.org, Andrey Ryabinin , "H. Peter Anvin" , Will Deacon , Marc Zyngier , Alistair Popple , Barry Song <21cnbao@gmail.com>, Matthew Wilcox , "Aneesh Kumar K.V" , Ingo Molnar , Zi Yan , "Naveen N. Rao" , John Hubbard , Nicholas Piggin , Borislav Petkov , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, James Morse , Andrew Morton , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 13/02/2024 14:08, Ard Biesheuvel wrote: > On Tue, 13 Feb 2024 at 15:05, David Hildenbrand wrote: >> >> On 13.02.24 15:02, Ryan Roberts wrote: >>> On 13/02/2024 13:45, David Hildenbrand wrote: >>>> On 13.02.24 14:33, Ard Biesheuvel wrote: >>>>> On Tue, 13 Feb 2024 at 14:21, Ryan Roberts wrote: >>>>>> >>>>>> On 13/02/2024 13:13, David Hildenbrand wrote: > ... >>>>>>> Just a thought, you could have a is_efi_mm() function that abstracts all that. >>>>>>> >>>>>>> diff --git a/include/linux/efi.h b/include/linux/efi.h >>>>>>> index c74f47711f0b..152f5fa66a2a 100644 >>>>>>> --- a/include/linux/efi.h >>>>>>> +++ b/include/linux/efi.h >>>>>>> @@ -692,6 +692,15 @@ extern struct efi { >>>>>>> >>>>>>> extern struct mm_struct efi_mm; >>>>>>> >>>>>>> +static inline void is_efi_mm(struct mm_struct *mm) >>>>>>> +{ >>>>>>> +#ifdef CONFIG_EFI >>>>>>> + return mm == &efi_mm; >>>>>>> +#else >>>>>>> + return false; >>>>>>> +#endif >>>>>>> +} >>>>>>> + >>>>>>> static inline int >>>>>>> efi_guidcmp (efi_guid_t left, efi_guid_t right) >>>>>>> { >>>>>>> >>>>>>> >>>>>> >>>>>> That would definitely work, but in that case, I might as well just check for it >>>>>> in mm_is_user() (and personally I would change the name to mm_is_efi()): >>>>>> >>>>>> >>>>>> static inline bool mm_is_user(struct mm_struct *mm) >>>>>> { >>>>>> return mm != &init_mm && !mm_is_efi(mm); >>>>>> } >>>>>> >>>>>> Any objections? >>>>>> >>>>> >>>>> Any reason not to use IS_ENABLED(CONFIG_EFI) in the above? The extern >>>>> declaration is visible to the compiler, and any references should >>>>> disappear before the linker could notice that efi_mm does not exist. >>>>> >>>> >>>> Sure, as long as the linker is happy why not. I'll let Ryan mess with that :) >>> >>> I'm not sure if you are suggesting dropping the mm_is_efi() helper and just use >>> IS_ENABLED(CONFIG_EFI) in mm_is_user() to guard efi_mm, or if you are suggesting >>> using IS_ENABLED(CONFIG_EFI) in mm_is_efi() instead of the ifdefery? >>> >>> The former was what I did initially; It works great, but I didn't like that I >>> was introducing a new code dependecy between efi and arm64 (nothing else outside >>> of efi references efi_mm). >>> >>> So then concluded that it is safe to not worry about efi_mm (thanks for your >>> confirmation). But then David wanted a VM_WARN check, which reintroduces the >>> code dependency. So he suggested the mm_is_efi() helper to hide that... This is >>> all starting to feel circular... >> >> I think Ard meant that inside mm_is_efi(), we could avoid the #ifdef and >> simply use IS_ENABLED(). >> > > Yes. > > static inline void mm_is_efi(struct mm_struct *mm) > { > return IS_ENABLED(CONFIG_EFI) && mm == &efi_mm; > } Ahh, got it. Yes, I'll do it like this. Thanks!