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To: Yuri Benditovich References: <20210609100457.142570-1-andrew@daynix.com> <3da88930-439c-1892-29b4-4977ddbb0b0a@redhat.com> <07a81543-c262-f153-6414-3d967dde02b2@redhat.com> From: Jason Wang Message-ID: <9157bf00-299f-993d-dd16-62f13e017a3f@redhat.com> Date: Tue, 22 Jun 2021 12:58:16 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jasowang@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Received-SPF: pass client-ip=170.10.133.124; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.373, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, 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: Andrew Melnichenko , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , "Michael S . Tsirkin" , toke@redhat.com, qemu-devel@nongnu.org, Markus Armbruster , Yan Vugenfirer , Eric Blake Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 在 2021/6/22 上午11:29, Yuri Benditovich 写道: > On Mon, Jun 21, 2021 at 12:20 PM Jason Wang wrote: >> >> 在 2021/6/19 上午4:03, Andrew Melnichenko 写道: >>> Hi Jason, >>> I've checked "kernel.unprivileged_bpf_disabled=0" on Fedora, Ubuntu, >>> and Debian - no need permissions to update BPF maps. >> >> How about RHEL :) ? > If I'm not mistaken, the RHEL releases do not use modern kernels yet > (for BPF we need 5.8+). > So this will be (probably) relevant for RHEL 9. Please correct me if I'm wrong. Adding Toke for more ideas on this. Thanks > > >> Thanks >> >> >>> On Wed, Jun 16, 2021 at 1:18 AM Andrew Melnichenko >> > wrote: >>> >>> Hi, >>> >>> I may miss something. >>> >>> But RSS requires to update the map. This won't work if you >>> don't grant >>> any permission to qemu. >>> >>> Thanks >>> >>> >>> Partly - with "kernel.unprivileged_bpf_disabled=0" capabilities is >>> not required to update maps. >>> With "kernel.unprivileged_bpf_disabled=1" - setting maps will >>> fail(without CAP_BPF) and "in-qemu" RSS will be used. >>> >>> On Tue, Jun 15, 2021 at 12:13 PM Jason Wang >> > wrote: >>> >>> >>> 在 2021/6/12 上午12:49, Andrew Melnichenko 写道: >>> > Hi, >>> > >>> > So I think the series is for unprivileged_bpf disabled. >>> If I'm not >>> > wrong, I guess the policy is to grant CAP_BPF but do >>> fine grain >>> > checks >>> > via LSM. >>> > >>> > >>> > The main idea is to run eBPF RSS with qemu without any >>> permission. >>> > Libvirt should handle everything and pass proper eBPF file >>> descriptors. >>> > For current eBPF RSS, CAP_SYS_ADMIN(bypass some limitations) >>> > also required, and in the future may be other permissions. >>> >>> >>> I may miss something. >>> >>> But RSS requires to update the map. This won't work if you >>> don't grant >>> any permission to qemu. >>> >>> Thanks >>> >>> >>> > >>> > I'm not sure this is the best. We have several examples >>> that let >>> > libvirt >>> > to involve. Examples: >>> > >>> > 1) create TAP device (and the TUN_SETIFF) >>> > >>> > 2) open vhost devices >>> > >>> > >>> > Technically TAP/vhost not related to a particular qemu >>> emulator. So common >>> > TAP creation should fit any modern qemu. eBPF fds(program >>> and maps) should >>> > suit the interface for current qemu, g.e. some qemu builds >>> may have >>> > different map >>> > structures or their count. It's necessary that the qemu got fds >>> > prepared by the helper >>> > that was built with the qemu. >>> > >>> > I think we need an example on the detail steps for how >>> libvirt is >>> > expected to use this. >>> > >>> > >>> > The simplified workflow looks like this: >>> > >>> > 1. Libvirt got "emulator" from domain document. >>> > 2. Libvirt queries for qemu capabilities. >>> > 3. One of the capabilities is "qemu-ebpf-rss-helper" >>> path(if present). >>> > 4. On NIC preparation Libvirt checks for virtio-net + rss >>> configurations. >>> > 5. If required, the "qemu-ebpf-rss-helper" called and fds are >>> > received through unix fd. >>> > 6. Those fds are for eBPF RSS, which passed to child >>> process - qemu. >>> > 7. Qemu launched with virtio-net-pci property "rss" and >>> "ebpf_rss_fds". >>> > >>> > >>> > On Fri, Jun 11, 2021 at 8:36 AM Jason Wang >>> >>> > >> >>> wrote: >>> > >>> > >>> > 在 2021/6/10 下午2:55, Yuri Benditovich 写道: >>> > > On Thu, Jun 10, 2021 at 9:41 AM Jason >>> Wang >>> > >> >> wrote: >>> > >> 在 2021/6/9 下午6:04, Andrew Melnychenko 写道: >>> > >>> Libvirt usually launches qemu with strict permissions. >>> > >>> To enable eBPF RSS steering, qemu-ebpf-rss-helper >>> was added. >>> > >> A silly question: >>> > >> >>> > >> Kernel had the following permission checks in bpf >>> syscall: >>> > >> >>> > >> if (sysctl_unprivileged_bpf_disabled && >>> !bpf_capable()) >>> > >> return -EPERM; >>> > >> ... >>> > >> >>> > >> err = security_bpf(cmd, &attr, size); >>> > >> if (err < 0) >>> > >> return err; >>> > >> >>> > >> So if I understand the code correctly, bpf syscall >>> can only be >>> > done if: >>> > >> >>> > >> 1) unprivileged_bpf is enabled or >>> > >> 2) has the capability and pass the LSM checks >>> > >> >>> > >> So I think the series is for unprivileged_bpf >>> disabled. If I'm not >>> > >> wrong, I guess the policy is to grant CAP_BPF but do >>> fine grain >>> > checks >>> > >> via LSM. >>> > >> >>> > >> If this is correct, need to describe it in the commit >>> log. >>> > >> >>> > >> >>> > >>> Added property "ebpf_rss_fds" for "virtio-net" that >>> allows to >>> > >>> initialize eBPF RSS context with passed program & >>> maps fds. >>> > >>> >>> > >>> Added qemu-ebpf-rss-helper - simple helper that >>> loads eBPF >>> > >>> context and passes fds through unix socket. >>> > >>> Libvirt should call the helper and pass fds to qemu >>> through >>> > >>> "ebpf_rss_fds" property. >>> > >>> >>> > >>> Added explicit target OS check for libbpf dependency >>> in meson. >>> > >>> eBPF RSS works only with Linux TAP, so there is no >>> reason to >>> > >>> build eBPF loader/helper for non-Linux. >>> > >>> >>> > >>> Overall, libvirt process should not be aware of the >>> "interface" >>> > >>> of eBPF RSS, it will not be aware of eBPF >>> maps/program "type" and >>> > >>> their quantity. >>> > >> I'm not sure this is the best. We have several >>> examples that >>> > let libvirt >>> > >> to involve. Examples: >>> > >> >>> > >> 1) create TAP device (and the TUN_SETIFF) >>> > >> >>> > >> 2) open vhost devices >>> > >> >>> > >> >>> > >>> That's why qemu and the helper should be from >>> > >>> the same build and be "synchronized". Technically >>> each qemu may >>> > >>> have its own helper. That's why "query-helper-paths" >>> qmp command >>> > >>> was added. Qemu should return the path to the helper >>> that suits >>> > >>> and libvirt should use "that" helper for "that" >>> emulator. >>> > >>> >>> > >>> qmp sample: >>> > >>> C: { "execute": "query-helper-paths" } >>> > >>> S: { "return": [ >>> > >>> { >>> > >>> "name": "qemu-ebpf-rss-helper", >>> > >>> "path": >>> "/usr/local/libexec/qemu-ebpf-rss-helper" >>> > >>> } >>> > >>> ] >>> > >>> } >>> > >> I think we need an example on the detail steps for >>> how libvirt is >>> > >> expected to use this. >>> > > The preliminary patches for libvirt are at >>> > > https://github.com/daynix/libvirt/tree/RSSv1 >>> >>> > >> > >>> > >>> > >>> > Will have a look but it would be better if the >>> assumption of the >>> > management is detailed here to ease the reviewers. >>> > >>> > Thanks >>> > >>> > >>> > > >>> > >>>