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 X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 080BDC433EF for ; Wed, 8 Sep 2021 14:16:23 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 78886610C9 for ; Wed, 8 Sep 2021 14:16:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 78886610C9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:40980 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mNyNB-0004nW-3E for qemu-devel@archiver.kernel.org; Wed, 08 Sep 2021 10:16:21 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:42526) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mNyIR-00088S-F6 for qemu-devel@nongnu.org; Wed, 08 Sep 2021 10:11:27 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:42813) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mNyIO-0008IO-Q4 for qemu-devel@nongnu.org; Wed, 08 Sep 2021 10:11:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1631110283; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=NOg26o5Z8jYznkKW+hOb5RkKD6p4RAISczwAwG75/sw=; b=N5/GqUYRznNHg8RNVdPhZUrhLIa9y9l4gc5Lw3DY+9h9nJ8OaM4DaLNN7nbaHQ4BzyBliL xpt+STlsFcWYBjLg/4xdKBqA8mv6kUrrDkW8zqEcFqoGJ4wpO4YRJPImgOnyknrzSELUGT bdHawk9wEWpCpKn+0dC2wBPYhWIRJyU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-482-dw-KyV-rOkKjdeFWqtdFWg-1; Wed, 08 Sep 2021 10:11:22 -0400 X-MC-Unique: dw-KyV-rOkKjdeFWqtdFWg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9DD9B1017965; Wed, 8 Sep 2021 14:11:21 +0000 (UTC) Received: from redhat.com (unknown [10.39.194.111]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AA77E5C1BB; Wed, 8 Sep 2021 14:11:20 +0000 (UTC) Date: Wed, 8 Sep 2021 16:11:19 +0200 From: Kevin Wolf To: Guillaume Roche Subject: Re: [PATCH] block/vvfat: Fix ro shared folder Message-ID: References: <20210831141727.347597-1-groche@genymobile.com> MIME-Version: 1.0 In-Reply-To: <20210831141727.347597-1-groche@genymobile.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.393, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Hanna Reitz , "open list:All patches CC here" , "open list:Block layer core" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 31.08.2021 um 16:17 hat Guillaume Roche geschrieben: > QEMU exits in error when passing a vfat shared folder in read-only mode. > > To fix this issue, this patch removes any potential write permission > from cumulative_perms, when a read-only block device is in use. > > Buglink: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=918950 > > Signed-off-by: Guillaume Roche > --- > This is an attempt to fix this behavior, but it feels a bit hacky to me > since this patch checks for the vvfat format in a generic function. > > However, I'd be glad to have some advice to make it better. Anyway, I > ran the block tests to ensure this does not introduce any regression. > > To add some context: I know that this can be worked around by setting > the shared folder in rw mode. But our use-case requires using both > shared and VM snapshots, and QEMU prevents using snapshot with a rw > shared folder. I don't think the behaviour is actually a bug: ide-hd requires a writable backend, so attaching a read-only vvfat node is a real error. You can either specify -drive read-only=on and use a device that can accept read-only backends (such as virtio-blk or ide-cd), or add a temporary writable qcow2 overlay with -snapshot or -drive snapshot=on so that the ide-hd device actually does get the writable backend it needs. Kevin