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Fri, 16 Apr 2021 11:33:33 +0200 (CEST) From: Markus Armbruster To: Li Zhang Subject: Re: [PATCH 2/2] Support monitor chardev hotswap with QMP References: <20210315170636.704201-1-zhlcindy@gmail.com> <20210315170636.704201-2-zhlcindy@gmail.com> <8735vu1ybo.fsf@dusky.pond.sub.org> Date: Fri, 16 Apr 2021 11:33:33 +0200 In-Reply-To: (Li Zhang's message of "Tue, 13 Apr 2021 10:51:12 +0200") Message-ID: <87a6py7evm.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) 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=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=216.205.24.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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: lukasstraub2@web.de, alexandr.iarygin@profitbricks.com, qemu-devel@nongnu.org, Li Zhang , pankaj.gupta@cloud.ionos.com, marcandre.lureau@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Li Zhang writes: > On Tue, Apr 13, 2021 at 8:41 AM Markus Armbruster wrote: >> >> Li Zhang writes: >> >> > From: Li Zhang >> > >> > For some scenarios, it needs to hot-add a monitor device. >> > But QEMU doesn't support hotplug yet. It also works by adding >> > a monitor with null backend by default and then change its >> > backend to socket by QMP command "chardev-change". >> > >> > So this patch is to support monitor chardev hotswap with QMP. >> > >> > Signed-off-by: Li Zhang >> >> I think what what you're trying to say is that chardev-change does not >> work when the character device changes is used by a QMP monitor. >> Correct? >> > I mean that when the character device is a monitor device, it doesn't > work with a QMP monitor. > For example, I add 2 QMP monitors and change one of the monitor's > backends from socket to a null device. > It doesn't work because it needs the monitor device to support chardev-change. > >> If yes, how exactly does it misbehave? > This command chardev-change needs specific device's change callback function. Yes, but what happens if you try anyway? I'm asking, because I'd like the answer to be worked into the commit message. >> Does it work with an HMP monitor? > No, it doesn't work.