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[2001:1c00:c32:7800:5bfa:a036:83f0:f9ec]) by smtp.gmail.com with ESMTPSA id se16-20020a170906ce5000b00a468be342bfsm2036173ejb.136.2024.03.24.07.49.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 24 Mar 2024 07:49:24 -0700 (PDT) Message-ID: Date: Sun, 24 Mar 2024 15:49:23 +0100 Precedence: bulk X-Mailing-List: linux-efi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: x86_64 32-bit EFI mixed mode boot broken To: Ard Biesheuvel , Clayton Craft Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , regressions@lists.linux.dev References: <20240321150510.GI8211@craftyguy.net> Content-Language: en-US, nl From: Hans de Goede In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi, On 3/21/24 11:48 PM, Ard Biesheuvel wrote: > (cc Hans) > > On Thu, 21 Mar 2024 at 23:05, Clayton Craft wrote: >> >> I've been chasing a problem with 32-bit EFI mixed mode booting on two different >> (x86_64) Intel Bay Trail platforms, where the system reboots or hangs seemingly >> very early somewhere before or after loading the kernel. I've not been able to >> get any output from the kernel or stub over efifb when the issue happens[0], and >> do not have serial console access on these systems. >> >> v6.8 fails for me, and presumably so does everything back to v6.2. v6.1 is able >> to boot OK on these platforms with mixed mode, and it looks like there are a lot >> of changes from 6.1..6.2 for EFI/mixed mode booting. > > v6.1 just received some EFI related backports, so please check the > latest v6.1.y as well. > >> I did managed to bisect the >> issue to: >> >> commit e2ab9eab324cdf240de89741e4a1aa79919f0196 >> Author: Ard Biesheuvel >> Date: Tue Nov 22 17:10:02 2022 +0100 >> >> x86/boot/compressed: Move 32-bit entrypoint code into .text section >> >> However I'm not sure how to proceed from here, or if my bisect is all that >> useful since the commit seems to be in the middle of a bunch of changes I do not >> understand. I've been using systemd-boot to test this (both the full bootloader >> and UKI w/ the sd-boot stub). Is 32-bit mixed mode on x86_64 working for others? >> > > I usually test on 32-bit OVMF built with LOAD_X64_ON_IA32_ENABLE, > which allows the use of the compat entry point. This is different from > the EFI handover protocol, and I am not sure which one you are using. > > I have never had any reports, or noticed any issues myself. Last time > I tried (some weeks ago) it was working for me. > CC'ing Hans who may have more data points. I've been offline for most of the week and I see that in the mean time you seem to have found a fix, great. FWIW I have been booting everything up to 6.8.0 on my own mixed-mode Bay Trail tablets without issues, so the problem seems to be specific to certain BIOS-es. Please Cc me on the final fix, then I can test that early and double check that things don't regress on other mixed-mode Bay Trail devices. Regards, Hans