From patchwork Wed Sep 16 09:51:49 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 305260 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=-9.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, 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 5E87FC43461 for ; Wed, 16 Sep 2020 10:04:20 +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 3C5492220E for ; Wed, 16 Sep 2020 10:04:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="USJMFd8a" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3C5492220E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:57226 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kIUIU-0005ne-6D for qemu-devel@archiver.kernel.org; Wed, 16 Sep 2020 06:04:18 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:53790) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kIU6t-0006BJ-Qr for qemu-devel@nongnu.org; Wed, 16 Sep 2020 05:52:19 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:58464) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kIU6r-0000du-Ri for qemu-devel@nongnu.org; Wed, 16 Sep 2020 05:52:19 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600249936; 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=UgsgLUowiBqZlz5+WiOQFwOsVeKJ0sRt4MwusZZWNVI=; b=USJMFd8aeH1SEHIMAI5SR7WHcjDSRqtnDxWsagGWuDgLTLOkDo/ICYoiCdk9+wGoaF9Ehy Xdt7p0yJSNcMyy94NQccz3kdrGkC4x21tmBtzt0lQCGqKc+W3vCv8dURmr8YHxw/Y7BtQ1 Xi0ABDOaokR+RXwJeenhc4tKPMy65Bg= 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-460-83ZCLrD9MBayvWt8Ww3O8g-1; Wed, 16 Sep 2020 05:52:15 -0400 X-MC-Unique: 83ZCLrD9MBayvWt8Ww3O8g-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 14E848030CB; Wed, 16 Sep 2020 09:52:14 +0000 (UTC) Received: from localhost (ovpn-115-47.ams2.redhat.com [10.36.115.47]) by smtp.corp.redhat.com (Postfix) with ESMTP id A976560BFA; Wed, 16 Sep 2020 09:52:07 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Subject: [PATCH v2 2/3] hostmem-file: add readonly=on|off option Date: Wed, 16 Sep 2020 10:51:49 +0100 Message-Id: <20200916095150.755714-3-stefanha@redhat.com> In-Reply-To: <20200916095150.755714-1-stefanha@redhat.com> References: <20200916095150.755714-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=stefanha@redhat.com X-Mimecast-Spam-Score: 0.002 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=63.128.21.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/16 02:35:56 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -50 X-Spam_score: -5.1 X-Spam_bar: ----- X-Spam_report: (-5.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.999, 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_H5=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: Eduardo Habkost , "Michael S. Tsirkin" , Julio Montes , Xiao Guangrong , eric.g.ernst@gmail.com, Stefan Hajnoczi , Igor Mammedov , Paolo Bonzini , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Let -object memory-backend-file work on read-only files when the readonly=on 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-Daudé Signed-off-by: Stefan Hajnoczi --- backends/hostmem-file.c | 26 +++++++++++++++++++++++++- qemu-options.hx | 5 ++++- 2 files changed, 29 insertions(+), 2 deletions(-) diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c index dffdf142e0..da585e4300 100644 --- a/backends/hostmem-file.c +++ b/backends/hostmem-file.c @@ -31,6 +31,7 @@ struct HostMemoryBackendFile { uint64_t align; bool discard_data; bool is_pmem; + bool readonly; }; static void @@ -58,7 +59,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **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 } @@ -153,6 +154,26 @@ static void file_memory_backend_set_pmem(Object *o, bool value, Error **errp) fb->is_pmem = value; } +static bool file_memory_backend_get_readonly(Object *o, Error **errp) +{ + return MEMORY_BACKEND_FILE(o)->readonly; +} + +static void file_memory_backend_set_readonly(Object *o, bool value, + Error **errp) +{ + HostMemoryBackend *backend = MEMORY_BACKEND(o); + HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o); + + if (host_memory_backend_mr_inited(backend)) { + error_setg(errp, "cannot change property 'readonly' of %s.", + object_get_typename(o)); + return; + } + + fb->readonly = value; +} + static void file_backend_unparent(Object *obj) { HostMemoryBackend *backend = MEMORY_BACKEND(obj); @@ -184,6 +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); } static void file_backend_instance_finalize(Object *o) diff --git a/qemu-options.hx b/qemu-options.hx index b0f020594e..3dfaaddd62 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -4369,7 +4369,7 @@ SRST they are specified. Note that the 'id' property must be set. These objects are placed in the '/objects' path. - ``-object memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|interleave,align=align`` + ``-object memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|interleave,align=align,readonly=on|off`` Creates a memory file backend object, which can be used to back the guest RAM with huge pages. @@ -4452,6 +4452,9 @@ SRST 4.15) and the filesystem of ``mem-path`` mounted with DAX option. + The ``readonly`` option specifies whether the backing file is opened + read-only or read-write (default). + ``-object memory-backend-ram,id=id,merge=on|off,dump=on|off,share=on|off,prealloc=on|off,size=size,host-nodes=host-nodes,policy=default|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