From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 92D4D4A1F for ; Mon, 19 Sep 2022 12:11:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68963C4347C for ; Mon, 19 Sep 2022 12:11:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1663589467; bh=iUvge7zWG1IaTHk8O9YyE4MFashXNW5X+EkroeGY7ko=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=VWZMXVuyVP3WAuSVsF+lLLZZ+UoLMSL3ajuWZfdBuky+TsjUVwVxReQExjngD4viJ uU68FZDS8W9BJHE/BMhojfWWsXtjzTivOXAldGYOJOLGX8714+K5zm9H/WVNzQdg8S VGWaf8sKJvWAiLOglvUzxa+6mSu6BvizZuVIcJJ8YadOMojzMEcUSNGwxb16ksiw5/ s0lajHzsDfRugj/tUGWAKPBFSQDazP+fJxcQoqCsudPdtCOoc9nPtXHwc68gTMHUgq BjQlqUZJTZ2/K3U3Si8mYatvoppLG462PDjlyjB6HkMCa3W3KO2p1Wkk8pDvlI5pQ9 d+McHtjcS+qow== Received: by mail-lf1-f41.google.com with SMTP id k10so46555983lfm.4 for ; Mon, 19 Sep 2022 05:11:07 -0700 (PDT) X-Gm-Message-State: ACrzQf0Y4qDihSJo5WsJhdlPok1/yhUFnzX2ET18v6EtIJGFov2N7Kfs U9gH1weWmUBobUFLzYWPNu7ywykURFri6zm52Nc= X-Google-Smtp-Source: AMsMyM6R3EpNQUFmF1TBioHNxqnu4e/C+L6MtJRzqt+ePvgglhHE/9dGp7/+ccuprwAaP5A8yv5YVdbuah3B/2N029A= X-Received: by 2002:ac2:4431:0:b0:497:aaf5:83eb with SMTP id w17-20020ac24431000000b00497aaf583ebmr5945626lfl.228.1663589465362; Mon, 19 Sep 2022 05:11:05 -0700 (PDT) Precedence: bulk X-Mailing-List: loongarch@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20220918213544.2176249-1-ardb@kernel.org> <20220918213544.2176249-12-ardb@kernel.org> In-Reply-To: From: Ard Biesheuvel Date: Mon, 19 Sep 2022 14:10:54 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 11/12] efi/loongarch: libstub: remove dependency on flattened DT To: Huacai Chen Cc: linux-efi , loongarch@lists.linux.dev, "Russell King (Oracle)" , Arnd Bergmann , Ilias Apalodimas , Huacai Chen , Xi Ruoyao Content-Type: text/plain; charset="UTF-8" On Mon, 19 Sept 2022 at 13:58, Huacai Chen wrote: > > On Mon, Sep 19, 2022 at 7:21 PM Ard Biesheuvel wrote: > > > > On Mon, 19 Sept 2022 at 13:15, Huacai Chen wrote: > > > > > > On Mon, Sep 19, 2022 at 6:49 PM Ard Biesheuvel wrote: > > > > > > > > On Mon, 19 Sept 2022 at 12:47, Huacai Chen wrote: > > > > > > > > > > On Mon, Sep 19, 2022 at 6:37 PM Ard Biesheuvel wrote: > > > > > > > > > > > > On Mon, 19 Sept 2022 at 12:33, Huacai Chen wrote: > > > > > > > > > > > > > > Hi, Ard, > > > > > > > > > > > > > > On Mon, Sep 19, 2022 at 2:22 PM Ard Biesheuvel wrote: > > > > > > > > > > > > > > > > On Mon, 19 Sept 2022 at 08:06, Huacai Chen wrote: > > > > > > > > > > > > > > > > > > Hi, Ard, > > > > > > > > > > > > > > > > > > On Mon, Sep 19, 2022 at 1:15 PM Ard Biesheuvel wrote: > > > > > > > > > > > > > > > > > > > > On Mon, 19 Sept 2022 at 03:58, Huacai Chen wrote: > > > > > > > > > > > > > > > > > > > > > > Hi, Ard, > > > > > > > > > > > > > > > > > > > > > > I think the parameters passed to the core kernel need to be discussed. > > > > > > > > > > > The old way (so-called old world): > > > > > > > > > > > a0=argc, a1=argv, a1=bpi > > > > > > > > > > > > > > > > > > > > > > The current way (so-called new world): > > > > > > > > > > > a0=efi boot flag, a1=fdt pointer > > > > > > > > > > > > > > > > > > > > > > The new way (in this patchset): > > > > > > > > > > > a0=efi boot flag, a1=systemtable, a2=cmdline > > > > > > > > > > > > > > > > > > > > > > I prefer to use the current way, there are 3 reasons: > > > > > > > > > > > 1, both acpi system and dt system can use the same parameters passing method; > > > > > > > > > > > > > > > > > > > > DT systems will use this too. The distinction is between EFI boot and > > > > > > > > > > non-EFI boot. We *really* should keep these separate, given the > > > > > > > > > > experience on ARM, where other projects invent ways to pass those > > > > > > > > > > values to the kernel without going through the stub. > > > > > > > > > In the last patch I see: > > > > > > > > > + void *fdt_ptr = early_memremap_ro(fw_arg1, SZ_64K); > > > > > > > > > + > > > > > > > > > + early_init_dt_scan(fdt_ptr); > > > > > > > > > + early_init_fdt_reserve_self(); > > > > > > > > > + > > > > > > > > > clear_bit(EFI_BOOT, &efi.flags); > > > > > > > > > So I suppose for the DT system that means a0=efi boot flag, a1=fdt > > > > > > > > > pointer, a2=cmdline? Then it is not exactly the same as the ACPI > > > > > > > > > system, but similar. > > > > > > > > > > > > > > > > > > > > > > > > > No, for non-EFI DT boot, the command line is passed via the DT, so > > > > > > > > a0=0x0 (non-efi), a1=DT, a2=0x0 > > > > > > > > > > > > > > > > Do you intend to support non-EFI DT boot by the way? > > > > > > > I think we needn't support non-EFI DT boot, so a0=efi boot flag, > > > > > > > a1=systemtable, a2=cmdline is just OK (or maybe we can exchange a1/a2, > > > > > > > which looks similar to the old-world). > > > > > > > > > > > > Excellent. If non-EFI boot is not supported, we can drop the code that > > > > > > deals with that. > > > > > > > > > > > > > But I have another question: is > > > > > > > it early enough to get DT from systemtable for DT boot (in the current > > > > > > > way DT is the earliest thing)? > > > > > > > > > > > > > > > > > > > If you rely on DT only for the hardware description, then loading it > > > > > > from efi_init() should be fine. > > > > > OK, then please drop patch #12 at this time. It can be added when we > > > > > add Loongson-2K support. > > > > > > > > > > > > > OK > > > > > > > > > > > > I don't think it makes sense to allow efi=novamap on LoongArch, given > > > > > > > > that we cannot make use of the runtime services that way. So in my > > > > > > > > code, efi_novamap is set to false unconditionally. > > > > > > > Emm, I prefer to support "efi=novamap", the core kernel has already > > > > > > > supported "noefi" to disable runtime, I don't want to hack > > > > > > > efi_novamap. So please keep the efi boot flag, thanks. > > > > > > > > > > > > > > > > > > > Fair enough. Do you have any uses for efi_novamap in mind? > > > > > I usually use "efi=novamap" in EFI shell to see whether it can work > > > > > well without runtime. And I think I will modify this patch these days > > > > > because in another thread you said that this series cannot boot. > > > > > > > > It works fine now. > > > > > > > > However, clearing the EFI_BOOT flag is not the correct way to disable > > > > runtime services only. And note that we also have efi=noruntime - does > > > > that currently work on LoongArch? > > > OK, but we don't need to add a new "efi=noruntime" parameter, I can > > > use "noefi" instead. > > > > OK > > > > > But I think support "efi=novamap" is not a bad > > > idea (maybe I misunderstood its usage). > > > > > > > It basically exists to deal with broken EFI firmware on ARM laptops > > that were only intended to run Windows. Windows calls > > SetVirtualAddressMap() *after* creating the new mappings, and some > > broken firmware drivers will access those regions too early. > > > > On Linux, we install the mapping first, and then much later, we > > actually create the mappings and only activate them on a single CPU > > while the EFI runtime service call is in progress. > > > > In any case, I will reinstate the efi_novamap logic for now - we can > > always revisit it later. > OK, now I think there are no big problems. Only some bikesheddings: > 1, Please use "a0=efi boot flag, a1=cmdline a2=systemtable" to pass > boot information, it looks most similar to the old-world, and we can > distinguish old-world/new-world by judging whether a0 is greater than > 1. > 2, I prefer "early return" in efi_init, i.e., if (boot_memmap == > EFI_INVALID_TABLE_ADDR) then return immediately, this makes > indentation look better. > 3, Declare "cmdline" out of the if() condition in init_environ() looks better. > 4, I prefer "kernel_addr" rather than "image_addr" in efi_boot_kernel(). > 5, It seems that one line is enough for the last statement in efi_boot_kernel(). > OK > Hope this series will be stable as soon as possible, our kexec/kdump > work needs to adjust because of this change. :) > Do you have a link to those patches?