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References: <20210713153758.323614-1-andrew@daynix.com> <20210713153758.323614-6-andrew@daynix.com> <87y29dct4m.fsf@dusky.pond.sub.org> <877dgbpco1.fsf@dusky.pond.sub.org> Date: Thu, 26 Aug 2021 06:53:45 +0200 In-Reply-To: (Andrew Melnichenko's message of "Wed, 25 Aug 2021 21:45:01 +0300") Message-ID: <87pmu03ixy.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 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: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.745, 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_H2=-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: "Daniel P. =?utf-8?Q?Berrang=C3=A9?=" , "Michael S. Tsirkin" , Jason Wang , qemu-devel@nongnu.org, Yuri Benditovich , Yan Vugenfirer , Eric Blake Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Andrew Melnichenko writes: > Hi, > Yes, the stamp check was added. > So the qemu emulator should return a suitable RSS BPF helper or nothing. > Each qemu emulator may have a different helper that suits it. > So, the idea is to ask for the helper from qemu. Please answer the question below. > > On Tue, Aug 24, 2021 at 9:41 AM Markus Armbruster wrote: > >> Andrew Melnichenko writes: >> >> > Hi, >> > >> >> The helper may or may not be installed at the path compiled into QEMU. >> >> >> > Yes, so the helper will not be called - QEMU will try to initiate eBPF >> RSS >> > or use "in-qemu" RSS. >> >> My point is: the proposed command's mission is to help the management >> application run the right helper. However, its advice is *unreliable*. >> It may point to the wrong helper, or to nothing at all. The right >> helper may still exist elsewhere. >> >> I suspect you're trying to address the problem at the wrong level. >> >> Similar versioning issues exist with other helpers. We've been doing >> fine without QEMU providing unreliable advice on where they might sit in >> the file system. What makes this one different? This one. >> >> What happens when you use the wrong helper? >> >> >> > UB - in most cases, eBPF program will work with wrong configurations. >> > That's why the stamp was added. >> > >> > query-helper-paths checks the stamp only for RSS helper. >> >> I have no idea what you're talking about :) >> >> My best guess is that you're trying to tell me that attempting to work >> with the wrong helper will fail cleanly due to some stamp check. That >> would be nice. >> >>