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[80.230.34.155]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4834d835f6bsm102408485e9.14.2026.02.11.01.37.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Feb 2026 01:37:01 -0800 (PST) Date: Wed, 11 Feb 2026 04:36:59 -0500 From: "Michael S. Tsirkin" To: Srujana Challa Cc: Jakub Kicinski , "netdev@vger.kernel.org" , "virtualization@lists.linux.dev" , "pabeni@redhat.com" , "jasowang@redhat.com" , "xuanzhuo@linux.alibaba.com" , "eperezma@redhat.com" , "davem@davemloft.net" , "edumazet@google.com" , Nithin Kumar Dabilpuram , Shiva Shankar Kommula Subject: Re: [EXTERNAL] Re: [PATCH v2 net-next] virtio_net: Improve RSS key size validation and use NETDEV_RSS_KEY_LEN Message-ID: <20260211043542-mutt-send-email-mst@kernel.org> References: <20260206120154.2548079-1-schalla@marvell.com> <20260206191308.7fdbfef4@kernel.org> <20260207045416-mutt-send-email-mst@kernel.org> <20260211030643-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: _ssTJCXWjyVlBDYCsEU1bd_d5sPy9ayIfwnX94qH0YA_1770802623 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Feb 11, 2026 at 09:33:26AM +0000, Srujana Challa wrote: > > On Wed, Feb 11, 2026 at 07:44:54AM +0000, Srujana Challa wrote: > > > > On Fri, Feb 06, 2026 at 07:13:08PM -0800, Jakub Kicinski wrote: > > > > > On Fri, 6 Feb 2026 17:31:54 +0530 Srujana Challa wrote: > > > > > > Replace hardcoded RSS max key size limit with NETDEV_RSS_KEY_LEN > > > > > > to align with kernel's standard RSS key length. Add validation > > > > > > for RSS key size against spec minimum (40 bytes) and driver > > > > > > maximum. When validation fails, gracefully disable RSS features > > > > > > and continue initialization rather than failing completely. > > > > > > > > > > Hm, FWIW clang says: > > > > > > > > > > drivers/net/virtio_net.c:6841:31: warning: result of comparison of > > > > > constant > > > > 256 with expression of type 'u8' (aka 'unsigned char') is always > > > > false [- Wtautological-constant-out-of-range-compare] > > > > > 6841 | } else if (vi->rss_key_size > > > VIRTIO_NET_RSS_MAX_KEY_SIZE) > > > > { > > > > > | ~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > > > > > > > > Which is kinda annoying because the value was increased in net-next. > > > > > If Machael wants this backported then we need to keep the check > > > > > and follow up in net-next? We could try to cast the u32 away but > > > > > that feels dirty.. > > > > > > > > > > > > I'd say yes. the warning is harmless. > > > > so > > > > patch 1 - this code > > > > patch 2 - replace with BUILD_BUG_ON > > > > > > > > but i ask then whether this code was actually tested against net-next. > > > Yes, tested against net-next (before NETDEV_RSS_KEY_LEN was changed to > > 256). > > > BUILD_BUG_ON would always fail as-is on net-next since rss_key_size is u8. > > > > BUILD_BUG_ON(type_max(vi->rss_key_size) >= > > VIRTIO_NET_RSS_MAX_KEY_SIZE) > > > > why would it fail? > I was assuming BUILD_BUG_ON was intended to catch the type mismatch > (when VIRTIO_NET_RSS_MAX_KEY_SIZE exceeds what u8 can hold). I understand > now - thanks for clarifying! maybe we should just #define VIRTIO_NET_RSS_MAX_KEY_SIZE type_max(vi->rss_key_size) + 1 > > > > > > > Can we cast the comparison to u32 instead? > > > Thanks! > > > > > > > > > > > -- > > > > MST > > > > > > > forcing compiler to generate code where we do not need any really seems silly. > > > > -- > > MST >