From nobody Mon Feb 9 17:25:29 2026 Delivered-To: importer@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+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1609780505; cv=none; d=zohomail.com; s=zohoarc; b=m2/Dj5exlqpKKtuTDj9kQEIgGgM3+H3whdNGHu84e1wJ8pA6Bgdd77nBWAseKoz5Me62GM0zgrdHLd4sc15mx6AzcKB+E158+WeoWLNyzZnph/4/28FsRDbg+o5gN4rUGmzY1RC1LA+4kbXSXFAIy9JD1wYj2SMxSOmizTEj1m8= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1609780505; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=JjgYdtXItrBRDuOEDu+e3r/gEkmIeLeFz46RVO5XZug=; b=UlimGLawTbRCTn6wTubm58xTnh9gIFhvnNkYoWs8+nxszSLPVb0PK8jJuaxS6pB4EPQwCa1DNPTodQYGZnH4KIXfx5czAiKbDmxZiQnlG2K879V3sKcmoJkWFoblbdCNmjbrdzX6Tsvpfp13iEHSmvd9p25IJi+ohX+fMjXAG4I= ARC-Authentication-Results: i=1; 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+importer=patchew.org@nongnu.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1609780505873343.00157041365117; Mon, 4 Jan 2021 09:15:05 -0800 (PST) Received: from localhost ([::1]:37258 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kwTRf-0003LU-Ts for importer@patchew.org; Mon, 04 Jan 2021 12:15:03 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:57398) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kwTQY-00020m-UP for qemu-devel@nongnu.org; Mon, 04 Jan 2021 12:13:55 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:55485) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kwTQS-0002SN-LK for qemu-devel@nongnu.org; Mon, 04 Jan 2021 12:13:54 -0500 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-75-NMpLlB24OieqIXwOyiqX5g-1; Mon, 04 Jan 2021 12:13:46 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C6E16C281; Mon, 4 Jan 2021 17:13:44 +0000 (UTC) Received: from localhost (ovpn-113-37.ams2.redhat.com [10.36.113.37]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8DCE25D735; Mon, 4 Jan 2021 17:13:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1609780428; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JjgYdtXItrBRDuOEDu+e3r/gEkmIeLeFz46RVO5XZug=; b=jKRLVZOt0XB7hBWrEs8NA5NSPzsJhz03qgA212/SaTZOJI1GaAJNLJ8rK2rHxEQMhk28rI Xqp6NgLJiknSR3P6UQaoShZ/UcuqlDgj0ol4vLCdtLgckMTZIrXrcqSehCQo0yO0rOcKZR 9jUD6PZT4F0855x4ZcBmi9bWEV9GWbM= X-MC-Unique: NMpLlB24OieqIXwOyiqX5g-1 From: Stefan Hajnoczi To: qemu-devel@nongnu.org Subject: [PATCH v3 2/3] hostmem-file: add readonly=on|off option Date: Mon, 4 Jan 2021 17:13:19 +0000 Message-Id: <20210104171320.575838-3-stefanha@redhat.com> In-Reply-To: <20210104171320.575838-1-stefanha@redhat.com> References: <20210104171320.575838-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=stefanha@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable 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+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=216.205.24.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.243, 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_H3=0.001, RCVD_IN_MSPIKE_WL=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: Xiao Guangrong , "Michael S. Tsirkin" , Julio Montes , Eduardo Habkost , eric.g.ernst@gmail.com, Stefan Hajnoczi , Igor Mammedov , Paolo Bonzini , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Richard Henderson Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Type: text/plain; charset="utf-8" Let -object memory-backend-file work on read-only files when the readonly=3Don option is given. This can be used to share the contents of a file between multiple guests while preventing them from consuming Copy-on-Write memory if guests dirty the pages, for example. Acked-by: Michael S. Tsirkin Reviewed-by: Philippe Mathieu-Daud=C3=A9 Reviewed-by: Liam Merwick Signed-off-by: Stefan Hajnoczi --- v3: * Use Object *obj instead of Object *o [Igor] * Do not dereference MEMORY_BACKEND_FILE(o)->readonly directly, use a local variable to hold the HostMemoryBackendFile pointer. [Igor] --- backends/hostmem-file.c | 28 +++++++++++++++++++++++++++- qemu-options.hx | 5 ++++- 2 files changed, 31 insertions(+), 2 deletions(-) diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c index e827692124..733408e076 100644 --- a/backends/hostmem-file.c +++ b/backends/hostmem-file.c @@ -29,6 +29,7 @@ struct HostMemoryBackendFile { uint64_t align; bool discard_data; bool is_pmem; + bool readonly; }; =20 static void @@ -56,7 +57,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Err= or **errp) backend->size, fb->align, (backend->share ? RAM_SHARED : 0) | (fb->is_pmem ? RAM_PMEM : 0), - fb->mem_path, false, errp); + fb->mem_path, fb->readonly, errp); g_free(name); #endif } @@ -151,6 +152,28 @@ static void file_memory_backend_set_pmem(Object *o, bo= ol value, Error **errp) fb->is_pmem =3D value; } =20 +static bool file_memory_backend_get_readonly(Object *obj, Error **errp) +{ + HostMemoryBackendFile *fb =3D MEMORY_BACKEND_FILE(obj); + + return fb->readonly; +} + +static void file_memory_backend_set_readonly(Object *obj, bool value, + Error **errp) +{ + HostMemoryBackend *backend =3D MEMORY_BACKEND(obj); + HostMemoryBackendFile *fb =3D MEMORY_BACKEND_FILE(obj); + + if (host_memory_backend_mr_inited(backend)) { + error_setg(errp, "cannot change property 'readonly' of %s.", + object_get_typename(obj)); + return; + } + + fb->readonly =3D value; +} + static void file_backend_unparent(Object *obj) { HostMemoryBackend *backend =3D MEMORY_BACKEND(obj); @@ -182,6 +205,9 @@ file_backend_class_init(ObjectClass *oc, void *data) NULL, NULL); object_class_property_add_bool(oc, "pmem", file_memory_backend_get_pmem, file_memory_backend_set_pmem); + object_class_property_add_bool(oc, "readonly", + file_memory_backend_get_readonly, + file_memory_backend_set_readonly); } =20 static void file_backend_instance_finalize(Object *o) diff --git a/qemu-options.hx b/qemu-options.hx index 459c916d3d..4732c6b45e 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -4407,7 +4407,7 @@ SRST they are specified. Note that the 'id' property must be set. These objects are placed in the '/objects' path. =20 - ``-object memory-backend-file,id=3Did,size=3Dsize,mem-path=3Ddir,share= =3Don|off,discard-data=3Don|off,merge=3Don|off,dump=3Don|off,prealloc=3Don|= off,host-nodes=3Dhost-nodes,policy=3Ddefault|preferred|bind|interleave,alig= n=3Dalign`` + ``-object memory-backend-file,id=3Did,size=3Dsize,mem-path=3Ddir,share= =3Don|off,discard-data=3Don|off,merge=3Don|off,dump=3Don|off,prealloc=3Don|= off,host-nodes=3Dhost-nodes,policy=3Ddefault|preferred|bind|interleave,alig= n=3Dalign,readonly=3Don|off`` Creates a memory file backend object, which can be used to back the guest RAM with huge pages. =20 @@ -4490,6 +4490,9 @@ SRST 4.15) and the filesystem of ``mem-path`` mounted with DAX option. =20 + The ``readonly`` option specifies whether the backing file is open= ed + read-only or read-write (default). + ``-object memory-backend-ram,id=3Did,merge=3Don|off,dump=3Don|off,shar= e=3Don|off,prealloc=3Don|off,size=3Dsize,host-nodes=3Dhost-nodes,policy=3Dd= efault|preferred|bind|interleave`` Creates a memory backend object, which can be used to back the guest RAM. Memory backend objects offer more control than the --=20 2.29.2