From nobody Mon May 12 07:49:57 2025 Delivered-To: importer2@patchew.org Authentication-Results: mx.zohomail.com; dkim=fail; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer2=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1695119639683890.7964857859973; Tue, 19 Sep 2023 03:33:59 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qiY16-0003vp-VW; Tue, 19 Sep 2023 06:31:41 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qiY0C-00036N-NS for qemu-devel@nongnu.org; Tue, 19 Sep 2023 06:30:45 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qiY0A-0001ud-JR for qemu-devel@nongnu.org; Tue, 19 Sep 2023 06:30:44 -0400 Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-647-tvckNiX2P-i9Qv9WKElDrA-1; Tue, 19 Sep 2023 06:30:40 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 14EAA1C05EAE; Tue, 19 Sep 2023 10:30:40 +0000 (UTC) Received: from t14s.redhat.com (unknown [10.39.194.89]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6A7B640C6EBF; Tue, 19 Sep 2023 10:30:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1695119441; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=yjkyeiLgHr2FDMto4R9a5D6A0D6S73stYv+FtlKwUfY=; b=V0Qb8nENP38jhYVrzFNGeeWQH7EKCn5GdBF9ACotd2KBpadkgWKS3OKbuIGnuwg3Smk3fz vJvFwzBAZIrcwcpscKBZhPwalcdOOei/8s+gGlGScXVfiuZ8/z8Wd+sy1G35/XJSOikP3y ppzxSTSuO4lx0651xaXeCMmy9gu0SOc= X-MC-Unique: tvckNiX2P-i9Qv9WKElDrA-1 From: David Hildenbrand To: qemu-devel@nongnu.org Cc: David Hildenbrand , ThinerLogoer Subject: [GIT PULL 10/12] softmmu/physmem: Hint that "readonly=on, rom=off" exists when opening file R/W for private mapping fails Date: Tue, 19 Sep 2023 12:30:27 +0200 Message-ID: <20230919103029.235736-11-david@redhat.com> In-Reply-To: <20230919103029.235736-1-david@redhat.com> References: <20230919103029.235736-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer2=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer2=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer2=patchew.org@nongnu.org X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZM-MESSAGEID: 1695119641637100005 Content-Type: text/plain; charset="utf-8" It's easy to miss that memory-backend-file with "share=3Doff" (default) will always try opening the file R/W as default, and fail if we don't have write permissions to the file. In that case, the user has to explicit specify "readonly=3Don,rom=3Doff" to get usable RAM, for example, for VM templating. Let's hint that '-object memory-backend-file,readonly=3Don,rom=3Doff,...' exists to consume R/O files in a private mapping to create writable RAM, but only if we have permissions to open the file read-only. Message-ID: <20230906120503.359863-11-david@redhat.com> Suggested-by: ThinerLogoer Signed-off-by: David Hildenbrand --- softmmu/physmem.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/softmmu/physmem.c b/softmmu/physmem.c index f1cd3ec28a..4f6ca653b3 100644 --- a/softmmu/physmem.c +++ b/softmmu/physmem.c @@ -1969,6 +1969,25 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, = MemoryRegion *mr, if (fd < 0) { error_setg_errno(errp, -fd, "can't open backing store %s for guest= RAM", mem_path); + if (!(ram_flags & RAM_READONLY_FD) && !(ram_flags & RAM_SHARED) && + fd =3D=3D -EACCES) { + /* + * If we can open the file R/O (note: will never create a new = file) + * and we are dealing with a private mapping, there are still = ways + * to consume such files and get RAM instead of ROM. + */ + fd =3D file_ram_open(mem_path, memory_region_name(mr), true, + &created); + if (fd < 0) { + return NULL; + } + assert(!created); + close(fd); + error_append_hint(errp, "Consider opening the backing store" + " read-only but still creating writable RAM using" + " '-object memory-backend-file,readonly=3Don,rom=3Doff...'" + " (see \"VM templating\" documentation)\n"); + } return NULL; } =20 --=20 2.41.0