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[54.240.197.234]) by smtp.gmail.com with ESMTPSA id o7-20020a05600c4fc700b003fefaf299b6sm24729wmq.38.2023.11.22.09.03.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Nov 2023 09:03:20 -0800 (PST) From: Paul Durrant X-Google-Original-From: Paul Durrant Message-ID: <02fcd3c2-afe2-43f4-8a15-7caa85a147f5@xen.org> Date: Wed, 22 Nov 2023 17:03:19 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/6] xen: backends: touch some XenStore nodes only if device... Content-Language: en-US To: Volodymyr Babchuk , "qemu-devel@nongnu.org" Cc: David Woodhouse , Stefano Stabellini , Julien Grall , Oleksandr Tyshchenko , Anthony Perard , Paul Durrant , Kevin Wolf , Hanna Reitz , =?UTF-8?Q?Marc-Andr=C3=A9_Lureau?= , Paolo Bonzini , Jason Wang , "open list:X86 Xen CPUs" , "open list:Block layer core" References: <20231121221023.419901-1-volodymyr_babchuk@epam.com> <20231121221023.419901-3-volodymyr_babchuk@epam.com> Organization: Xen Project In-Reply-To: <20231121221023.419901-3-volodymyr_babchuk@epam.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2a00:1450:4864:20::234; envelope-from=xadimgnik@gmail.com; helo=mail-lj1-x234.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: paul@xen.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 21/11/2023 22:10, Volodymyr Babchuk wrote: > was created by QEMU > > Xen PV devices in QEMU can be created in two ways: either by QEMU > itself, if they were passed via command line, or by Xen toolstack. In > the latter case, QEMU scans XenStore entries and configures devices > accordingly. > > In the second case we don't want QEMU to write/delete front-end > entries for two reasons: it might have no access to those entries if > it is running in un-privileged domain and it is just incorrect to > overwrite entries already provided by Xen toolstack, because toolstack > manages those nodes. For example, it might read backend- or frontend- > state to be sure that they are both disconnected and it is safe to > destroy a domain. > > This patch checks presence of xendev->backend to check if Xen PV > device is acting as a backend (i.e. it was configured by Xen Technally *all* XenDevice objects are backends. > toolstack) to decide if it should touch frontend entries in XenStore. > Also, when we need to remove XenStore entries during device teardown > only if they weren't created by Xen toolstack. If they were created by > toolstack, then it is toolstack's job to do proper clean-up. >