From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 917BB64A8D for ; Fri, 17 Jul 2026 04:16:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784261793; cv=none; b=a3x1Q85lTlqGJBmG77p8E1qJv9vfD/lDz1MZIaczPg4LXIO4MYvx88jeDl50D4JP6rG1H8244/8uKasza1x7MhEA/kMLmSqw1emX3j/yxo3abCyVS6jpfEHpf0pw5sxqjelW0958wgcOKbZOtP2byVan2FXqIiK2w4al7CAbdFo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784261793; c=relaxed/simple; bh=qbRRlxOtRN6hWppRiqfYwDql1OvoKXqkARDwBGDBgBY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=N84DZJgKqZSjmTE8HCSYRzjw4yLX8Ag/71yy8oPWzpPRHPPzHU0WHu2+llw+gwnQQ+o8iiTG9O+vj4rdtv0ZZI/FBMDjGHzxLj9Zfsp2xg39xMYJxM/74K1CKFZIgbIuTPtzmiLykTNQq+fZmiAgNBNRKNs3OxKW1yu5QKDXvXM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=BBQA1azI; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="BBQA1azI" 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 207651476; Thu, 16 Jul 2026 21:16:25 -0700 (PDT) Received: from [10.164.18.90] (unknown [10.164.18.90]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 562023F7D8; Thu, 16 Jul 2026 21:16:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1784261789; bh=qbRRlxOtRN6hWppRiqfYwDql1OvoKXqkARDwBGDBgBY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=BBQA1azIq5p20nHyKyJX1ATjKM0CRuIaUkF0sGkJBbdJ7Cf55ezLmUl3KBCpVimjA y9Dv4lsQnL9UOtMFVZdlDyCENDDHnXXEaGnRIcaNtCngwdFrOqb+LGcgeU5UkBgwQJ 0/m1kIKdvfx2hl9pVtPkU+DK372qUVeyxRQfxmI0= Message-ID: <8f512add-b78f-49df-9239-274e7a9558ea@arm.com> Date: Fri, 17 Jul 2026 09:46:24 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64/defconfig: Restore built-in 9P rootfs support To: Arnd Bergmann , Krzysztof Kozlowski , linux-arm-kernel@lists.infradead.org Cc: Eric Biggers , Linus Walleij , Alexandre Belloni , linux-kernel@vger.kernel.org References: <20260716100243.1604526-1-anshuman.khandual@arm.com> <2fae9ef8-2ec1-48ed-9b25-8526db625732@oss.qualcomm.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 16/07/26 5:01 PM, Arnd Bergmann wrote: > On Thu, Jul 16, 2026, at 13:01, Krzysztof Kozlowski wrote: >> On 16/07/2026 12:02, Anshuman Khandual wrote: >>> Commit d521c4ca039f ("arm64: defconfig: Switch Ethernet drivers to modules") >>> had changed 9P and virtio-9P support from built-in to modular instead. This >>> breaks simple kvmtool boots using a 9P root filesystem without an initramfs >>> , because the kernel must mount root filesystem before it can load the 9P >> >> >> And that commit explained you must use initramfs. Nothing got broken, >> because there was never a promise that a recent, virtualized environment >> must work on defconfig without initramfs. >> >> You fully control your software, so just build initramfs which is >> absolutely trivial and we all moved on to that for arm64 long time ago. > > I still regularly boot KVM guests on arm64 without an initramfs, Actually that is a very normal use case particularly with KVM tool. > but I just use 'make kvm_guest.config', which turns on all the > commonly used virtio drivers as built-in. I wouldn't call > 9pfs root trivial without initramfs, configuring 9p built-in > is already complicated enough. Alright - fair enough. > > So I agree we don't need this patch, but there is a trivial > workaround for Anshuman in case he wants to avoid doing this. The following sequence does indeed solve this problem for now. make mrproper make defconfig make kvm_guest.config