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bh=BBFmHW/hskTQGqFHdrpkVNS/QUPIu1bLyKfDfQNSiSs=; b=bF8yfRwwZv8dnZTAoWLfV0qMx1g2RsNREIb4bJWoHs5/ttQUHov4ydzwOMSPBZcS13HHaI VqWezX1JhccB7YvknHREgnC6Q4d2TUIx5rMA1QBGm7GDZNa49jhxQsXOcibOewYA0zUebT bzY5CJ+U4oDNXIVbi50J5dW9cYVpI5w= 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-518-J3vP7BfiNDu4vGuaE0Z64Q-1; Fri, 15 Jan 2021 04:36:09 -0500 X-MC-Unique: J3vP7BfiNDu4vGuaE0Z64Q-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 76B1F1922028 for ; Fri, 15 Jan 2021 09:36:08 +0000 (UTC) Received: from [10.40.194.52] (unknown [10.40.194.52]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7A44C5C1A3; Fri, 15 Jan 2021 09:36:07 +0000 (UTC) Subject: Re: [PATCH v2] machine: add missing doc for memory-backend option To: Igor Mammedov , qemu-devel@nongnu.org References: <20210114234612.795621-1-imammedo@redhat.com> From: Michal Privoznik Message-ID: Date: Fri, 15 Jan 2021 10:36:05 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20210114234612.795621-1-imammedo@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mprivozn@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=mprivozn@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -32 X-Spam_score: -3.3 X-Spam_bar: --- X-Spam_report: (-3.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.248, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.237, 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: pbonzini@redhat.com, pkrempa@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 1/15/21 12:46 AM, Igor Mammedov wrote: > Add documentation for '-machine memory-backend' CLI option and > how to use it. > > And document that x-use-canonical-path-for-ramblock-id, > is considered to be stable to make sure it won't go away by accident. > > Signed-off-by: Igor Mammedov > --- > v2: > - add doc that x-use-canonical-path-for-ramblock-id is considered stable, > (Peter Krempa ) > --- > backends/hostmem.c | 10 ++++++++++ > qemu-options.hx | 28 +++++++++++++++++++++++++++- > 2 files changed, 37 insertions(+), 1 deletion(-) > > @@ -96,6 +97,31 @@ SRST > ``hmat=on|off`` > Enables or disables ACPI Heterogeneous Memory Attribute Table > (HMAT) support. The default is off. > + > + ``memory-backend='id'`` > + An alternative to legacy ``-mem-path`` and ``mem-prealloc`` options. > + Allows to use a memory backend as main RAM. > + > + For example: > + :: > + -object memory-backend-file,id=pc.ram,size=512M,mem-path=/hugetlbfs,prealloc=on,share=on > + -machine memory-backend=pc.ram > + -m 512M > + > + Migration compatibility note: > + a) as backend id one shall use value of 'default-ram-id', advertised 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=on`` backend option > + (this option must be considered stable, as if it didn't have the 'x-' > + prefix including deprecation period, as long as 4.0 and older machine > + types exists), > + if migration to/from old QEMU (<5.0) is expected. > + For example: > + :: > + -object memory-backend-ram,id=pc.ram,size=512M,x-use-canonical-path-for-ramblock-id=on > + -machine memory-backend=pc.ram > + -m 512M Igor, this doesn't correspond with your comment in bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1836043#c31 In fact, we had to turn the attribute OFF so that canonical path is not used. Isn't ON the default state anyway? Michal