From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 39FE64483AB for ; Fri, 11 Sep 2026 08:21:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789114869; cv=none; b=EwN2zqMpefP3yIBw9n5LxDZW7ugfJ1dzW2jzFV+mVwvaLMHqKCYO8589uJKqtPOpUl4GRBycFv1H6lZAgGDRSp/daEhuNV2zlzhpzhgrD2PHdKVRPIdlPvMz4uYfSR7HnCjYrvxxC86WfVfGdu9z8Lqe1Tll4APMWHW2Kihbw6Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789114869; c=relaxed/simple; bh=D4Y6DZ5elql50SecTlmUNxc51hoasK2HjVQ9HwfDSfk=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=GctPytRtWjZRrKP4DrPzpNCSqELu2a0oEUMLA9sIM5UCetkxlrCs+qahslZTVWFDJR1IzXbIUnB/CQ2qKs3RIEtSFebkTfy8BL9KLCWRljpSlq3FBOrpRV0FlwZ2CKAaeWLhuJmnZzCN4c5DyVc3RABs/yP1T1J+02oT1B5Yp34= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JGGcin70; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JGGcin70" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9191D1F000FF; Fri, 11 Sep 2026 08:21:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789114867; bh=I6zPl3vs4A3X1cJMBm5TbAtH8Nab/AustytvAreNHMU=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=JGGcin70o7erocN7xBtfJrBAf2g73aDx8WBnWRFTT0Ec23K2dRQ/dBafdT0TWI0g+ jGNQrOPEPoK3RFwvR4nfw7xw144HcE1oKtS3XbyVjZ4YJDVfCgTlpD8+XpEUtO9eSr Eyr71P6HB1fJLpnUqngyajzuj2NZpkbhfw96rHHayn+p69MrStdN+f65VrSS6cmvqw iZiqrOdDJdYFqWhFwd0/+QfIgLUkn16RlmzUTxKWLcAly2eElsap/7MDb9jaeNJYbX VRmr+M9i/DFUSgZWpmXgpieBEACi5aN92S/Pk1k5mP1LuA0ZNiH2Z/H23Q0WbL7R81 0gGBMbKdiF00A== From: sashiko-bot@kernel.org Subject: Re: [PATCH] virtio_pci_modern: fall back to 64 bits features for devices without an extended features space Reply-To: sashiko-reviews@lists.linux.dev To: "Peng Hao" Cc: virtualization@lists.linux.dev, "Michael S. Tsirkin" , "Eugenio Perez" In-Reply-To: <20260911081133.16434-1-flyingpeng@tencent.com> References: <20260911081133.16434-1-flyingpeng@tencent.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 11 Sep 2026 08:21:07 +0000 Message-Id: <20260911082107.9191D1F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: > From: Peng Hao >=20 > Since commit 69b9461512246 ("virtio_pci_modern: allow configuring > extended features") the modern virtio-pci driver unconditionally > accesses the whole 128 bits features space, i.e. it drives > device_feature_select / guest_feature_select with the values 0..3. >=20 > Devices predating the extended features space only implement the > legacy 64 bits one, and what they report for the selectors above it is > not a valid features space. Negotiating it makes the driver and the > device end up with different features sets: on a smart NIC exposing a > virtio_net device the link comes up but carries no traffic, while the > same device works with a kernel that only accesses the low 64 bits. >=20 > Reading the features space has no side effect, so keep reading all of > [ ... ] > Conforming devices are unaffected: their extended words are neither > all-ones nor an alias of the low ones, so the detection does not > trigger. >=20 > Signed-off-by: Peng Hao Sashiko has reviewed this patch and found no issues. It looks great! --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260911081133.1643= 4-1-flyingpeng@tencent.com?part=3D1