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bh=aGiRvX/miiDra234/3N3CmVjK/lJzDKYceY/6z9WJE8=; b=CVdKox/ZS7qRepxacCRNnykoHd9RouUKOUDHL8jrc/CBpy3Tj0QF6sXkb8oHLEK/D05rUd PW8bydgUK0nK/jD7XiDdbQ9iRkVBcOeizDerDB/HdbOGg+6jwOsrnhV2brYzzaI+REBE8Q 4MtQNSzABFyXnyLm623luvm3aZg9g5A= X-MC-Unique: wdoEUUNeNSGxKnGM6sCnUA-1 From: Eduardo Habkost To: Peter Maydell , qemu-devel@nongnu.org Subject: [PULL 2/3] hostmem-file: add readonly=on|off option Date: Tue, 2 Feb 2021 14:30:19 -0500 Message-Id: <20210202193020.4107711-3-ehabkost@redhat.com> In-Reply-To: <20210202193020.4107711-1-ehabkost@redhat.com> References: <20210202193020.4107711-1-ehabkost@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=ehabkost@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="utf-8" 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=63.128.21.124; envelope-from=ehabkost@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=-0.386, 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_H4=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: Igor Mammedov , "Michael S . Tsirkin" , Stefan Hajnoczi , Paolo Bonzini , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) From: Stefan Hajnoczi 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. Signed-off-by: Stefan Hajnoczi Reviewed-by: Philippe Mathieu-Daud=C3=A9 Reviewed-by: Liam Merwick Acked-by: Michael S. Tsirkin Message-Id: <20210104171320.575838-3-stefanha@redhat.com> Signed-off-by: Eduardo Habkost --- 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 e8276921244..733408e076f 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 d0410f05125..c09c4646e28 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -4426,7 +4426,7 @@ 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 @@ -4509,6 +4509,9 @@ 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 2.28.0