From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from layka.disroot.org (layka.disroot.org [178.21.23.139]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F3E0E2E973B for ; Tue, 12 Aug 2025 09:43:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.21.23.139 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754991811; cv=none; b=k3cLO7Y6sXQoNbXXMSloM8OZEYnVKmbCb+uFMmPbd5ahH4CZO3yziBpAQSORNnxH6l2a41ebmfhJqcDO8tz04uU243B762wnZ8vRJHUSO1ga0NHlbnGj/81pvQpccY1guUEWXGo67VvoxVHKfo+5cHxj+hUPq/l/TZyzwBDv7vU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754991811; c=relaxed/simple; bh=VoQtnN8TVNFZ35OF82gYJyQyCQWCWSyi54UG/5Pr244=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=NJkPyj9E1DO35jA0b/f06EpBuGLukMxiDc5C156vbHoS4Z4QGefpN6ke/4eQbbkBqP1/zhAonwPn1DEtneSuuAtPGTvs8URmCEQOAaQHkOGC8PpHGxfYhSZCnB7QrcK7S77JxTypl8hfSaCDvG54zeS5iv8puNoHEAizIpZjZwY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=disroot.org; spf=pass smtp.mailfrom=disroot.org; dkim=pass (2048-bit key) header.d=disroot.org header.i=@disroot.org header.b=c2tx00vQ; arc=none smtp.client-ip=178.21.23.139 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=disroot.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=disroot.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=disroot.org header.i=@disroot.org header.b="c2tx00vQ" Received: from mail01.disroot.lan (localhost [127.0.0.1]) by disroot.org (Postfix) with ESMTP id 31DAF2588F; Tue, 12 Aug 2025 11:43:26 +0200 (CEST) X-Virus-Scanned: SPAM Filter at disroot.org Received: from layka.disroot.org ([127.0.0.1]) by localhost (disroot.org [127.0.0.1]) (amavis, port 10024) with ESMTP id JUhdKEmfHZPA; Tue, 12 Aug 2025 11:43:25 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=disroot.org; s=mail; t=1754991805; bh=VoQtnN8TVNFZ35OF82gYJyQyCQWCWSyi54UG/5Pr244=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=c2tx00vQAKJGnzvzuLEMjpjeoaNpI1Lx0c3Y8cYCtqN4lEKdCwFGNrqXbwho96cDr De1FkMyLuefVDZ+EHP+/XKNmUy4XwSfPWGEiUj93BWfM8qh+seZfrg7OLRBKdPtyho 4xOzvuxmCq4q8r348zHFgM9DXNb1lhhU+ALeaggJj6kTqFkH06UOrLRRFxk6VbWsCj DUqEitM07Olvng7ttQyjj6AkbsX8m+F+Oc/nN0EuOqWpP+mKScI++CAojssp9JPQli bbNjTsLkTOQd6peyhyYtg9f+LfX6Uczqd3MoJV8BVGu3raF2pAoBrESbufbZwQR9ey qHp4TQ/TBwk3g== Date: Tue, 12 Aug 2025 09:43:13 +0000 From: Yao Zi To: Youling Tang , Huacai Chen Cc: WANG Xuerui , Baoquan He , kexec@lists.infradead.org, loongarch@lists.linux.dev, linux-kernel@vger.kernel.org, Youling Tang Subject: Re: [PATCH 2/6] LoongArch: Add kexec_file support Message-ID: References: <20250811092659.14903-1-youling.tang@linux.dev> <20250811092659.14903-3-youling.tang@linux.dev> <6de97571-7ef0-4bbd-b55f-5ad41898a6ec@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Aug 12, 2025 at 03:06:23PM +0800, Youling Tang wrote: > On 2025/8/12 14:15, Youling Tang wrote: > > Hi, Yao > > On 2025/8/12 01:06, Yao Zi wrote: > > > On Mon, Aug 11, 2025 at 05:26:55PM +0800, Youling Tang wrote: > > > > From: Youling Tang > > > > > > > > This patch adds support for kexec_file on LoongArch. > > > > > > > > The image_load() as two parts: > > > > - the first part loads the kernel image (vmlinuz.efi or vmlinux.efi) > > > > - the second part loads other segments (eg: initrd, cmdline) > > > > > > > > Currently, pez(vmlinuz.efi) and pei(vmlinux.efi) format images > > > > are supported, > > > > but ELF format is not supported. > > > > > > > > Signed-off-by: Youling Tang > > > > --- > > > >   arch/loongarch/Kconfig                     |   8 ++ > > > >   arch/loongarch/include/asm/image.h         |  18 ++++ > > > >   arch/loongarch/include/asm/kexec.h         |  12 +++ > > > >   arch/loongarch/kernel/Makefile             |   1 + > > > >   arch/loongarch/kernel/kexec_image.c        | 112 > > > > +++++++++++++++++++++ > > > >   arch/loongarch/kernel/machine_kexec.c      |  33 ++++-- > > > >   arch/loongarch/kernel/machine_kexec_file.c |  46 +++++++++ > > > >   7 files changed, 219 insertions(+), 11 deletions(-) > > > >   create mode 100644 arch/loongarch/kernel/kexec_image.c > > > >   create mode 100644 arch/loongarch/kernel/machine_kexec_file.c ... > > > > diff --git a/arch/loongarch/kernel/kexec_image.c > > > > b/arch/loongarch/kernel/kexec_image.c > > > > new file mode 100644 > > > > index 000000000000..fdd1845b4e2e > > > > --- /dev/null > > > > +++ b/arch/loongarch/kernel/kexec_image.c ... > > > > +    /* > > > > +     * The location of the kernel segment may make it > > > > impossible to satisfy > > > > +     * the other segment requirements, so we try repeatedly to find a > > > > +     * location that will work. > > > > +     */ > > > > +    while ((ret = kexec_add_buffer(&kbuf)) == 0) { > > > > +        /* Try to load additional data */ > > > > +        kernel_segment = &image->segment[kernel_segment_number]; > > > > +        ret = load_other_segments(image, kernel_segment->mem, > > > > +                      kernel_segment->memsz, initrd, > > > > +                      initrd_len, cmdline, cmdline_len); > > > > +        if (!ret) > > > > +            break; > > > > + > > > > +        /* > > > > +         * We couldn't find space for the other segments; erase the > > > > +         * kernel segment and try the next available hole. > > > > +         */ > > > > +        image->nr_segments -= 1; > > > > +        kbuf.buf_min = kernel_segment->mem + kernel_segment->memsz; > > > > +        kbuf.mem = KEXEC_BUF_MEM_UNKNOWN; > > > > +    } > > > > + > > > > +    if (ret) { > > > > +        pr_err("Could not find any suitable kernel location!"); > > > > +        return ERR_PTR(ret); > > > > +    } > > > > + > > > > +    kernel_segment = &image->segment[kernel_segment_number]; > > > > + > > > > +    /* Make sure the second kernel jumps to the correct > > > > "kernel_entry". */ > > > > +    image->start = kernel_segment->mem + h->kernel_entry - > > > > text_offset; > > > A non-relocatable loongarch kernel cannot be loaded to arbitrary > > > address. Thus this loading function seems to only work for relocatable > > > kernels, maybe it's better to leave a comment indicating the limitation. > > > > > > For now, we don't seem to have a way to find out whether the kernel is > > > relocatable (for example, a flag in kernel image header), so it's > > > impossible to point out whether the loaded kernel boots fine with > > > arbitrary loading address... > > LoongArch enables the relocation of the kernel when the kdump > > feature is enabled. > > > > config ARCH_SELECTS_CRASH_DUMP > >         def_bool y > >         depends on CRASH_DUMP > >         select RELOCATABLE > > This only means the currently-running kernel is relocatable, not the one being exec'ed, right? > When enabling KEXEC_FILE, the RELOCATABLE configuration should > also be enabled. Both kexec and kdump require this. I'm not sure whether you're talking about the running kernel or the one that is going to be exec'ed. This method of kernel loading requires the exec'ed kernel being relocatable, not the currently running one. And I think it's totally reasonable to use KEXEC_FILE for non-crash-dump purpose, for example, linuxboot. It'll be confusing to the user if the system just hangs after booting a non-relocatable kernel, which is hard to debug. Thus IMHO we should ideally refuse to load non-relocatable kernels, or add a FIXME comment to indicate the situation that it's impossible to determine whether the exec'ed image is relocatable. > Youling. > > After enabling the relocation, LoongArch is the PIE kernel. For > > more details, please refer to commit d8da19fbdedd ("LoongArch: > > Add support for kernel relocation") Best regards. Yao Zi