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([2a01:e0a:e10:ef90:343a:68f:2e91:95c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42fa8a70440sm5759024f8f.16.2025.12.11.05.26.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Dec 2025 05:26:01 -0800 (PST) Message-ID: Date: Thu, 11 Dec 2025 14:26:01 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 4/6] vhost-user: Add queue pair parameter throughout the network stack To: Stefano Brivio References: <20251203185435.582096-1-lvivier@redhat.com> <20251203185435.582096-5-lvivier@redhat.com> <20251211080144.72d9577f@elisabeth> <85c1c222-dbd6-410d-96e3-9b000795919f@redhat.com> <20251211131618.1b5dac57@elisabeth> From: Laurent Vivier Autocrypt: addr=lvivier@redhat.com; keydata= xsFNBFYFJhkBEAC2me7w2+RizYOKZM+vZCx69GTewOwqzHrrHSG07MUAxJ6AY29/+HYf6EY2 WoeuLWDmXE7A3oJoIsRecD6BXHTb0OYS20lS608anr3B0xn5g0BX7es9Mw+hV/pL+63EOCVm SUVTEQwbGQN62guOKnJJJfphbbv82glIC/Ei4Ky8BwZkUuXd7d5NFJKC9/GDrbWdj75cDNQx UZ9XXbXEKY9MHX83Uy7JFoiFDMOVHn55HnncflUncO0zDzY7CxFeQFwYRbsCXOUL9yBtqLer Ky8/yjBskIlNrp0uQSt9LMoMsdSjYLYhvk1StsNPg74+s4u0Q6z45+l8RAsgLw5OLtTa+ePM JyS7OIGNYxAX6eZk1+91a6tnqfyPcMbduxyBaYXn94HUG162BeuyBkbNoIDkB7pCByed1A7q q9/FbuTDwgVGVLYthYSfTtN0Y60OgNkWCMtFwKxRaXt1WFA5ceqinN/XkgA+vf2Ch72zBkJL RBIhfOPFv5f2Hkkj0MvsUXpOWaOjatiu0fpPo6Hw14UEpywke1zN4NKubApQOlNKZZC4hu6/ 8pv2t4HRi7s0K88jQYBRPObjrN5+owtI51xMaYzvPitHQ2053LmgsOdN9EKOqZeHAYG2SmRW LOxYWKX14YkZI5j/TXfKlTpwSMvXho+efN4kgFvFmP6WT+tPnwARAQABzSNMYXVyZW50IFZp dmllciA8bHZpdmllckByZWRoYXQuY29tPsLBeAQTAQIAIgUCVgVQgAIbAwYLCQgHAwIGFQgC CQoLBBYCAwECHgECF4AACgkQ8ww4vT8vvjwpgg//fSGy0Rs/t8cPFuzoY1cex4limJQfReLr SJXCANg9NOWy/bFK5wunj+h/RCFxIFhZcyXveurkBwYikDPUrBoBRoOJY/BHK0iZo7/WQkur 6H5losVZtrotmKOGnP/lJYZ3H6OWvXzdz8LL5hb3TvGOP68K8Bn8UsIaZJoeiKhaNR0sOJyI YYbgFQPWMHfVwHD/U+/gqRhD7apVysxv5by/pKDln1I5v0cRRH6hd8M8oXgKhF2+rAOL7gvh jEHSSWKUlMjC7YwwjSZmUkL+TQyE18e2XBk85X8Da3FznrLiHZFHQ/NzETYxRjnOzD7/kOVy gKD/o7asyWQVU65mh/ECrtjfhtCBSYmIIVkopoLaVJ/kEbVJQegT2P6NgERC/31kmTF69vn8 uQyW11Hk8tyubicByL3/XVBrq4jZdJW3cePNJbTNaT0d/bjMg5zCWHbMErUib2Nellnbg6bc 2HLDe0NLVPuRZhHUHM9hO/JNnHfvgiRQDh6loNOUnm9Iw2YiVgZNnT4soUehMZ7au8PwSl4I KYE4ulJ8RRiydN7fES3IZWmOPlyskp1QMQBD/w16o+lEtY6HSFEzsK3o0vuBRBVp2WKnssVH qeeV01ZHw0bvWKjxVNOksP98eJfWLfV9l9e7s6TaAeySKRRubtJ+21PRuYAxKsaueBfUE7ZT 7zfOwU0EVgUmGQEQALxSQRbl/QOnmssVDxWhHM5TGxl7oLNJms2zmBpcmlrIsn8nNz0rRyxT 460k2niaTwowSRK8KWVDeAW6ZAaWiYjLlTunoKwvF8vP3JyWpBz0diTxL5o+xpvy/Q6YU3BN efdq8Vy3rFsxgW7mMSrI/CxJ667y8ot5DVugeS2NyHfmZlPGE0Nsy7hlebS4liisXOrN3jFz asKyUws3VXek4V65lHwB23BVzsnFMn/bw/rPliqXGcwl8CoJu8dSyrCcd1Ibs0/Inq9S9+t0 VmWiQWfQkz4rvEeTQkp/VfgZ6z98JRW7S6l6eophoWs0/ZyRfOm+QVSqRfFZdxdP2PlGeIFM C3fXJgygXJkFPyWkVElr76JTbtSHsGWbt6xUlYHKXWo+xf9WgtLeby3cfSkEchACrxDrQpj+ Jt/JFP+q997dybkyZ5IoHWuPkn7uZGBrKIHmBunTco1+cKSuRiSCYpBIXZMHCzPgVDjk4viP brV9NwRkmaOxVvye0vctJeWvJ6KA7NoAURplIGCqkCRwg0MmLrfoZnK/gRqVJ/f6adhU1oo6 z4p2/z3PemA0C0ANatgHgBb90cd16AUxpdEQmOCmdNnNJF/3Zt3inzF+NFzHoM5Vwq6rc1JP jfC3oqRLJzqAEHBDjQFlqNR3IFCIAo4SYQRBdAHBCzkM4rWyRhuVABEBAAHCwV8EGAECAAkF AlYFJhkCGwwACgkQ8ww4vT8vvjwg9w//VQrcnVg3TsjEybxDEUBm8dBmnKqcnTBFmxN5FFtI WlEuY8+YMiWRykd8Ln9RJ/98/ghABHz9TN8TRo2b6WimV64FmlVn17Ri6FgFU3xNt9TTEChq AcNg88eYryKsYpFwegGpwUlaUaaGh1m9OrTzcQy+klVfZWaVJ9Nw0keoGRGb8j4XjVpL8+2x OhXKrM1fzzb8JtAuSbuzZSQPDwQEI5CKKxp7zf76J21YeRrEW4WDznPyVcDTa+tz++q2S/Bp P4W98bXCBIuQgs2m+OflERv5c3Ojldp04/S4NEjXEYRWdiCxN7ca5iPml5gLtuvhJMSy36gl U6IW9kn30IWuSoBpTkgV7rLUEhh9Ms82VWW/h2TxL8enfx40PrfbDtWwqRID3WY8jLrjKfTd R3LW8BnUDNkG+c4FzvvGUs8AvuqxxyHbXAfDx9o/jXfPHVRmJVhSmd+hC3mcQ+4iX5bBPBPM oDqSoLt5w9GoQQ6gDVP2ZjTWqwSRMLzNr37rJjZ1pt0DCMMTbiYIUcrhX8eveCJtY7NGWNyx FCRkhxRuGcpwPmRVDwOl39MB3iTsRighiMnijkbLXiKoJ5CDVvX5yicNqYJPKh5MFXN1bvsB kmYiStMRbrD0HoY1kx5/VozBtc70OU0EB8Wrv9hZD+Ofp0T3KOr1RUHvCZoLURfFhSQ= In-Reply-To: <20251211131618.1b5dac57@elisabeth> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 8FoYJ5zTYZNGGCqu_HmO_pxEnee1_u7Fve1VkX9BZEY_1765459563 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Message-ID-Hash: GDEDN23JPMZ25JOJSSD5YZEAKUV62R6C X-Message-ID-Hash: GDEDN23JPMZ25JOJSSD5YZEAKUV62R6C X-MailFrom: lvivier@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On 12/11/25 13:16, Stefano Brivio wrote: > On Thu, 11 Dec 2025 09:48:42 +0100 > Laurent Vivier wrote: > >> On 12/11/25 08:01, Stefano Brivio wrote: >>> On Wed, 3 Dec 2025 19:54:32 +0100 >>> Laurent Vivier wrote: >>> >>>> diff --git a/vu_common.c b/vu_common.c >>>> index b13b7c308fd8..80d9a30f6f71 100644 >>>> --- a/vu_common.c >>>> +++ b/vu_common.c >>>> @@ -196,11 +196,11 @@ static void vu_handle_tx(struct vu_dev *vdev, int index, >>>> >>>> data = IOV_TAIL(elem[count].out_sg, elem[count].out_num, 0); >>>> if (IOV_DROP_HEADER(&data, struct virtio_net_hdr_mrg_rxbuf)) >>>> - tap_add_packet(vdev->context, &data, now); >>>> + tap_add_packet(vdev->context, 0, &data, now); >>>> >>>> count++; >>>> } >>>> - tap_handler(vdev->context, now); >>>> + tap_handler(vdev->context, 0, now); >>>> >>>> if (count) { >>>> int i; >>>> @@ -235,23 +235,26 @@ void vu_kick_cb(struct vu_dev *vdev, union epoll_ref ref, >>>> } >>>> >>>> /** >>>> - * vu_send_single() - Send a buffer to the front-end using the RX virtqueue >>>> + * vu_send_single() - Send a buffer to the front-end using a specified virtqueue >>>> * @c: execution context >>>> + * @qpair: Queue pair on which to send the buffer >>>> * @buf: address of the buffer >>>> * @size: size of the buffer >>>> * >>>> * Return: number of bytes sent, -1 if there is an error >>>> */ >>>> -int vu_send_single(const struct ctx *c, const void *buf, size_t size) >>>> +int vu_send_single(const struct ctx *c, unsigned int qpair, const void *buf, size_t size) >>>> { >>>> struct vu_dev *vdev = c->vdev; >>>> - struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE]; >>>> struct vu_virtq_element elem[VIRTQUEUE_MAX_SIZE]; >>>> struct iovec in_sg[VIRTQUEUE_MAX_SIZE]; >>>> + struct vu_virtq *vq; >>>> size_t total; >>>> int elem_cnt; >>>> int i; >>>> >>>> + vq = &vdev->vq[qpair << 1]; >>> >>> << 1 instead of * 2 is a bit surprising here, for a few seconds I >>> thought you swapped qpair and 1. >>> >>> Then I started thinking that somebody is likely to mix up (probably not >>> you) indices of RX and TX queues at some point. So... what about some >>> macros, say (let's see if I got it right this time): >>> >>> #define VHOST_SEND_QUEUE(pair) ((pair) * 2) >>> #define VHOST_RECV_QUEUE(pair) (pair) >> >> I will. David had the same comment. > > Uh, wait, I must have missed it. Do you have a Message-ID? I'm afraid I > must have missed some emails here but I don't see them in archives > either... Message-ID: aRF1_Qj6uxf1ndiA@zatzit >> TX and RX are from the point of view of guest, it's >> not obvious when we read passt code. > > Right, yes, for me neither, I always get confused. That's why I thought > we could make the RX vhost-user queue become "SEND" in passt's code, > but: > >> I would prefer as David proposed to use, i.e. FROMGUEST and TOGUEST: >> >> #define VHOST_FROM_GUEST(qpair) ((qpair) * 2 + 1) >> #define VHOST_TO_GUEST(qpair) ((qpair) * 2) > > ...this is even clearer. It misses the QUEUE though. Does > VHOST_QUEUE_{FROM,TO}_GUEST fit where you use it? Otherwise I guess VQ > together with FROM / TO should be clear enough. > >>> and: >>> >>> #define VHOST_QUEUE_PAIR(q) ((q) % 2) ? (q) : (q) / 2) >> >> I don't undestand the purpose of this one. > > To get the pair number from a queue number. You're doing something like > that (I guess?) in 5/6, vu_handle_tx(): > > + tap_flush_pools(index / 2); > > + tap_add_packet(vdev->context, index / 2, &data, now); > > + tap_handler(vdev->context, index / 2, now); > > but now that I see your definition for VHOST_FROM_GUEST() above, and > that the purpose wasn't clear to you, I guess it should be: > > #define VHOST_PAIR_FROM_QUEUE(q) (((q) % 2) ? ((q) - 1 / 2) : ((q) / 2)) > Why not simply: #define VHOST_PAIR_FROM_QUEUE(q) (q / 2) QUEUES 0,1 -> QP 0 QUEUES 2,3 -> QP 1 > ...or maybe it's not needed? I'm not sure. > >>> >>> ...are they correct? A short description or "Theory of operation" >>> section somewhere with a recap of how queue indices are used would be >>> nice to have. >>> >>> And maybe also something explaining that 0 that's now appearing in >>> argument lists: >>> >>> #define VHOST_NO_QUEUE 0 >> >> It's not really NO_QUEUE, it's default queue pair, the queue pair 0 > > Hmm but for non-vhost-user usages then it's not a queue, right? Well, For non vhost usage we can say there is only one queue. > whatever, as long as we have a definition for it... or maybe we could > have VHOST_QUEUE_DEFAULT and NO_VHOST_QUEUE or VHOST_NO_QUEUE all being > 0? > Perhaps we could instead use a generic naming: QPAIR_DEFAULT QUEUE_FROM_GUEST(qpair) QUEUE_TO_GUEST(qpair) Thanks, Laurent