From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id B8FB943F01; Thu, 25 Apr 2024 15:44:46 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id A3DC9435F4; Thu, 25 Apr 2024 15:44:46 +0200 (CEST) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by mails.dpdk.org (Postfix) with ESMTP id 1E37140284 for ; Thu, 25 Apr 2024 15:44:45 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1714052684; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=Nq3OJKOONSkNhh2+TnUs4BN4NAh/7c2GuKEjUsJAHVc=; b=OVaa96/7btKEIrMMYsBRUOuxckABc/QmbPpDr0lP+MicnG0PmvjAv6K4oHYXl7VuCYl85K fXZ71gNCISkDhk4fEvxymlG1a8KT0nR/cPJgLrRLf2K5A3qfmZzwtWqRqCQLPCFCVLugO2 bDZiH4KPAA6PdKWa22UGsaMLeK8U644= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-221-NP9XbV8wPwmav5kDpEi3aw-1; Thu, 25 Apr 2024 09:44:40 -0400 X-MC-Unique: NP9XbV8wPwmav5kDpEi3aw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BF56E2932480; Thu, 25 Apr 2024 13:44:39 +0000 (UTC) Received: from [10.39.208.23] (unknown [10.39.208.23]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 776B65C5CC7; Thu, 25 Apr 2024 13:44:38 +0000 (UTC) Message-ID: Date: Thu, 25 Apr 2024 15:44:37 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] vhost: fix GCC 13 build error To: Luca Vizzarro , dev@dpdk.org Cc: luca.boccassi@gmail.com, paul.szczepanek@arm.com, nick.connolly@arm.com, stable@dpdk.org References: <20240410152101.3211244-1-luca.vizzarro@arm.com> <20240410152101.3211244-2-luca.vizzarro@arm.com> From: Maxime Coquelin Autocrypt: addr=maxime.coquelin@redhat.com; keydata= xsFNBFOEQQIBEADjNLYZZqghYuWv1nlLisptPJp+TSxE/KuP7x47e1Gr5/oMDJ1OKNG8rlNg kLgBQUki3voWhUbMb69ybqdMUHOl21DGCj0BTU3lXwapYXOAnsh8q6RRM+deUpasyT+Jvf3a gU35dgZcomRh5HPmKMU4KfeA38cVUebsFec1HuJAWzOb/UdtQkYyZR4rbzw8SbsOemtMtwOx YdXodneQD7KuRU9IhJKiEfipwqk2pufm2VSGl570l5ANyWMA/XADNhcEXhpkZ1Iwj3TWO7XR uH4xfvPl8nBsLo/EbEI7fbuUULcAnHfowQslPUm6/yaGv6cT5160SPXT1t8U9QDO6aTSo59N jH519JS8oeKZB1n1eLDslCfBpIpWkW8ZElGkOGWAN0vmpLfdyiqBNNyS3eGAfMkJ6b1A24un /TKc6j2QxM0QK4yZGfAxDxtvDv9LFXec8ENJYsbiR6WHRHq7wXl/n8guyh5AuBNQ3LIK44x0 KjGXP1FJkUhUuruGyZsMrDLBRHYi+hhDAgRjqHgoXi5XGETA1PAiNBNnQwMf5aubt+mE2Q5r qLNTgwSo2dpTU3+mJ3y3KlsIfoaxYI7XNsPRXGnZi4hbxmeb2NSXgdCXhX3nELUNYm4ArKBP LugOIT/zRwk0H0+RVwL2zHdMO1Tht1UOFGfOZpvuBF60jhMzbQARAQABzSxNYXhpbWUgQ29x dWVsaW4gPG1heGltZS5jb3F1ZWxpbkByZWRoYXQuY29tPsLBeAQTAQIAIgUCV3u/5QIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQyjiNKEaHD4ma2g/+P+Hg9WkONPaY1J4AR7Uf kBneosS4NO3CRy0x4WYmUSLYMLx1I3VH6SVjqZ6uBoYy6Fs6TbF6SHNc7QbB6Qjo3neqnQR1 71Ua1MFvIob8vUEl3jAR/+oaE1UJKrxjWztpppQTukIk4oJOmXbL0nj3d8dA2QgHdTyttZ1H xzZJWWz6vqxCrUqHU7RSH9iWg9R2iuTzii4/vk1oi4Qz7y/q8ONOq6ffOy/t5xSZOMtZCspu Mll2Szzpc/trFO0pLH4LZZfz/nXh2uuUbk8qRIJBIjZH3ZQfACffgfNefLe2PxMqJZ8mFJXc RQO0ONZvwoOoHL6CcnFZp2i0P5ddduzwPdGsPq1bnIXnZqJSl3dUfh3xG5ArkliZ/++zGF1O wvpGvpIuOgLqjyCNNRoR7cP7y8F24gWE/HqJBXs1qzdj/5Hr68NVPV1Tu/l2D1KMOcL5sOrz 2jLXauqDWn1Okk9hkXAP7+0Cmi6QwAPuBT3i6t2e8UdtMtCE4sLesWS/XohnSFFscZR6Vaf3 gKdWiJ/fW64L6b9gjkWtHd4jAJBAIAx1JM6xcA1xMbAFsD8gA2oDBWogHGYcScY/4riDNKXi lw92d6IEHnSf6y7KJCKq8F+Jrj2BwRJiFKTJ6ChbOpyyR6nGTckzsLgday2KxBIyuh4w+hMq TGDSp2rmWGJjASrOwU0EVPSbkwEQAMkaNc084Qvql+XW+wcUIY+Dn9A2D1gMr2BVwdSfVDN7 0ZYxo9PvSkzh6eQmnZNQtl8WSHl3VG3IEDQzsMQ2ftZn2sxjcCadexrQQv3Lu60Tgj7YVYRM H+fLYt9W5YuWduJ+FPLbjIKynBf6JCRMWr75QAOhhhaI0tsie3eDsKQBA0w7WCuPiZiheJaL 4MDe9hcH4rM3ybnRW7K2dLszWNhHVoYSFlZGYh+MGpuODeQKDS035+4H2rEWgg+iaOwqD7bg CQXwTZ1kSrm8NxIRVD3MBtzp9SZdUHLfmBl/tLVwDSZvHZhhvJHC6Lj6VL4jPXF5K2+Nn/Su CQmEBisOmwnXZhhu8ulAZ7S2tcl94DCo60ReheDoPBU8PR2TLg8rS5f9w6mLYarvQWL7cDtT d2eX3Z6TggfNINr/RTFrrAd7NHl5h3OnlXj7PQ1f0kfufduOeCQddJN4gsQfxo/qvWVB7PaE 1WTIggPmWS+Xxijk7xG6x9McTdmGhYaPZBpAxewK8ypl5+yubVsE9yOOhKMVo9DoVCjh5To5 aph7CQWfQsV7cd9PfSJjI2lXI0dhEXhQ7lRCFpf3V3mD6CyrhpcJpV6XVGjxJvGUale7+IOp sQIbPKUHpB2F+ZUPWds9yyVxGwDxD8WLqKKy0WLIjkkSsOb9UBNzgRyzrEC9lgQ/ABEBAAHC wV8EGAECAAkFAlT0m5MCGwwACgkQyjiNKEaHD4nU8hAAtt0xFJAy0sOWqSmyxTc7FUcX+pbD KVyPlpl6urKKMk1XtVMUPuae/+UwvIt0urk1mXi6DnrAN50TmQqvdjcPTQ6uoZ8zjgGeASZg jj0/bJGhgUr9U7oG7Hh2F8vzpOqZrdd65MRkxmc7bWj1k81tOU2woR/Gy8xLzi0k0KUa8ueB iYOcZcIGTcs9CssVwQjYaXRoeT65LJnTxYZif2pfNxfINFzCGw42s3EtZFteczClKcVSJ1+L +QUY/J24x0/ocQX/M1PwtZbB4c/2Pg/t5FS+s6UB1Ce08xsJDcwyOPIH6O3tccZuriHgvqKP yKz/Ble76+NFlTK1mpUlfM7PVhD5XzrDUEHWRTeTJSvJ8TIPL4uyfzhjHhlkCU0mw7Pscyxn DE8G0UYMEaNgaZap8dcGMYH/96EfE5s/nTX0M6MXV0yots7U2BDb4soLCxLOJz4tAFDtNFtA wLBhXRSvWhdBJZiig/9CG3dXmKfi2H+wdUCSvEFHRpgo7GK8/Kh3vGhgKmnnxhl8ACBaGy9n fxjSxjSO6rj4/MeenmlJw1yebzkX8ZmaSi8BHe+n6jTGEFNrbiOdWpJgc5yHIZZnwXaW54QT UhhSjDL1rV2B4F28w30jYmlRmm2RdN7iCZfbyP3dvFQTzQ4ySquuPkIGcOOHrvZzxbRjzMx1 Mwqu3GQ= In-Reply-To: <20240410152101.3211244-2-luca.vizzarro@arm.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On 4/10/24 17:21, Luca Vizzarro wrote: > This patch resolves a build error with GCC 13 and arm/aarch32 as > targets: > > In function ‘mbuf_to_desc’, > inlined from ‘vhost_enqueue_async_packed’ at > ../lib/vhost/virtio_net.c:1828:6, > inlined from ‘virtio_dev_rx_async_packed’ at > ../lib/vhost/virtio_net.c:1842:6, > inlined from ‘virtio_dev_rx_async_submit_packed’ at > ../lib/vhost/virtio_net.c:1900:7: > ../lib/vhost/virtio_net.c:1159:18: error: ‘buf_vec[0].buf_addr’ may > be used uninitialized [-Werror=maybe-uninitialized] > 1159 | buf_addr = buf_vec[vec_idx].buf_addr; > | ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~ > > ../lib/vhost/virtio_net.c:1160:18: error: ‘buf_vec[0].buf_iova’ may > be used uninitialized [-Werror=maybe-uninitialized] > 1160 | buf_iova = buf_vec[vec_idx].buf_iova; > | ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~ > > ../lib/vhost/virtio_net.c:1161:35: error: ‘buf_vec[0].buf_len’ may > be used uninitialized [-Werror=maybe-uninitialized] > 1161 | buf_len = buf_vec[vec_idx].buf_len; > | ~~~~~~~~~~~~~~~~^~~~~~~~ > > GCC complains about the possible runtime path where the while loop > which fills buf_vec (in vhost_enqueue_async_packed) is not run. As a > consequence it correctly thinks that buf_vec is not initialized while > being accessed anyways. > > This scenario is actually very unlikely as the only way this can occur > is if size has overflowed to 0. Meaning that the total packet length > would be close to UINT64_MAX (or actually UINT32_MAX). At first glance, > the code suggests that this may never happen as the type of size has > been changed to 64-bit. For a 32-bit architecture such as arm > (e.g. armv7-a) and aarch32, this still happens because the operand types > (pkt->pkt_len and sizeof) are 32-bit wide, performing 32-bit arithmetic > first (where the overflow can happen) and widening to 64-bit later. > > The proposed fix simply guarantees to the compiler that the scope which > fills buf_vec is accessed at least once, while not disrupting the actual > logic. This is based on the assumption that size will always be greater > than 0, as suggested by the sizeof, and the packet length will never be > as big as UINT32_MAX, and causing an overflow. > > Fixes: 873e8dad6f49 ("vhost: support packed ring in async datapath") > Cc: stable@dpdk.org > > Signed-off-by: Luca Vizzarro > Reviewed-by: Paul Szczepanek > Reviewed-by: Nick Connolly > --- > lib/vhost/virtio_net.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > Reviewed-by: Maxime Coquelin Thanks, Maxime