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bh=MF5rvtI35B6c1TYwVYEa0qfgvJ1qe6vHr2nTdT8GSeU=; b=IOaXbM4kW/3DgH9WJnm6aYOHoBapKHFKvvFEELZs2WJB7VzqFar19x1EVgarWuRGXiFcuC YVXvOwxO9NMvL2TcGEw6JQEhFkOIwv6tqsIp3iHsYw6wvIf1YcEOGcr8yHnIgT03t8/ZlM mjXHlRDCA/CRllT4weBjlsI0iJuQ06s= X-MC-Unique: Vjg65gWCOwGayaupQd2G4Q-1 From: Igor Mammedov To: qemu-devel@nongnu.org Subject: [PATCH] machine: add missing doc for memory-backend option Date: Mon, 11 Jan 2021 17:27:29 -0500 Message-Id: <20210111222729.757402-1-imammedo@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=imammedo@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=63.128.21.124; envelope-from=imammedo@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=-0.251, 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: mprivozn@redhat.com, ehabkost@redhat.com, pbonzini@redhat.com 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" Add documentation for '-machine memory-backend' CLI option and how to use it. PS: While at it add a comment to x-use-canonical-path-for-ramblock-id, to make sure it won't go away by accident. Signed-off-by: Igor Mammedov Reviewed-by: Michal Privoznik --- backends/hostmem.c | 8 ++++++++ qemu-options.hx | 25 ++++++++++++++++++++++++- 2 files changed, 32 insertions(+), 1 deletion(-) diff --git a/backends/hostmem.c b/backends/hostmem.c index 4bde00e8e7..f6f4e818c7 100644 --- a/backends/hostmem.c +++ b/backends/hostmem.c @@ -497,6 +497,14 @@ host_memory_backend_class_init(ObjectClass *oc, void *= data) host_memory_backend_get_share, host_memory_backend_set_share); object_class_property_set_description(oc, "share", "Mark the memory as private to QEMU or shared"); + /* + * Do not delete/rename option till 4.0 and older machine types exist, + * Option will be used by upper layers to override (disable) canonical= path + * for ramblock-id set by compat properties on old machine types ( <= =3D 4.0), + * to keep migration working when backend is used for main RAM with + * -machine memory-backend=3D option (main RAM historically used prefi= x-less + * ramblock-id). + */ object_class_property_add_bool(oc, "x-use-canonical-path-for-ramblock-= id", host_memory_backend_get_use_canonical_path, host_memory_backend_set_use_canonical_path); diff --git a/qemu-options.hx b/qemu-options.hx index 459c916d3d..c02628bd26 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -35,7 +35,8 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \ " suppress-vmdesc=3Don|off disables self-describing mig= ration (default=3Doff)\n" " nvdimm=3Don|off controls NVDIMM support (default=3Dof= f)\n" " memory-encryption=3D@var{} memory encryption object t= o use (default=3Dnone)\n" - " hmat=3Don|off controls ACPI HMAT support (default=3Do= ff)\n", + " hmat=3Don|off controls ACPI HMAT support (default=3Do= ff)\n" + " memory-backend=3D'backend-id' specifies explicitly pr= ovided backend for main RAM (default=3Dnone)\n", QEMU_ARCH_ALL) SRST ``-machine [type=3D]name[,prop=3Dvalue[,...]]`` @@ -96,6 +97,28 @@ SRST ``hmat=3Don|off`` Enables or disables ACPI Heterogeneous Memory Attribute Table (HMAT) support. The default is off. + + ``memory-backend=3D'id'`` + An alternative to legacy ``-mem-path`` and ``mem-prealloc`` option= s. + Allows to use a memory backend as main RAM. + + For example: + :: + -object memory-backend-file,id=3Dpc.ram,size=3D512M,mem-path=3D/hu= getlbfs,prealloc=3Don,share=3Don + -machine memory-backend=3Dpc.ram + -m 512M + + Migration compatibility note: + a) as backend id one shall use value of 'default-ram-id', advertis= ed by + machine type (available via ``query-machines`` QMP command) + b) for machine types 4.0 and older, user shall + use ``x-use-canonical-path-for-ramblock-id=3Don`` backend option, + if migration to/from old QEMU (<5.0) is expected. + For example: + :: + -object memory-backend-ram,id=3Dpc.ram,size=3D512M,x-use-canonical= -path-for-ramblock-id=3Don + -machine memory-backend=3Dpc.ram + -m 512M ERST =20 HXCOMM Deprecated by -machine --=20 2.27.0