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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-20794735719sm24738385ad.275.2024.09.15.12.48.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 15 Sep 2024 12:48:37 -0700 (PDT) Date: Sun, 15 Sep 2024 12:48:35 -0700 From: Stephen Hemminger To: Akihiko Odaki Cc: Jonathan Corbet , Willem de Bruijn , Jason Wang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "Michael S. Tsirkin" , Xuan Zhuo , Shuah Khan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kselftest@vger.kernel.org, Yuri Benditovich , Andrew Melnychenko Subject: Re: [PATCH RFC v3 0/9] tun: Introduce virtio-net hashing feature Message-ID: <20240915124835.456676f0@hermes.local> In-Reply-To: <20240915-rss-v3-0-c630015db082@daynix.com> References: <20240915-rss-v3-0-c630015db082@daynix.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sun, 15 Sep 2024 10:17:39 +0900 Akihiko Odaki wrote: > virtio-net have two usage of hashes: one is RSS and another is hash > reporting. Conventionally the hash calculation was done by the VMM. > However, computing the hash after the queue was chosen defeats the > purpose of RSS. > > Another approach is to use eBPF steering program. This approach has > another downside: it cannot report the calculated hash due to the > restrictive nature of eBPF. > > Introduce the code to compute hashes to the kernel in order to overcome > thse challenges. > > An alternative solution is to extend the eBPF steering program so that it > will be able to report to the userspace, but it is based on context > rewrites, which is in feature freeze. We can adopt kfuncs, but they will > not be UAPIs. We opt to ioctl to align with other relevant UAPIs (KVM > and vhost_net). This will be useful for DPDK. But there still are cases where custom flow rules are needed. I.e the RSS happens after other TC rules. It would be a good if skbedit supported RSS as an option.