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([2a01:e0a:e10:ef90:343a:68f:2e91:95c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45a1e136360sm7419835e9.18.2025.08.14.02.02.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 Aug 2025 02:02:57 -0700 (PDT) Message-ID: <84f40250-6c5c-48ae-a02b-52720d9cb455@redhat.com> Date: Thu, 14 Aug 2025 11:02:57 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 30/30] packet: Add support for multi-vector packets To: David Gibson References: <20250805154628.301343-31-lvivier@redhat.com> 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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: GLlhmZcNlJXbH6yBkGkB8pXlBPMe8sfHrjR6v75PJrE_1755162180 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: 7QAUNG3GDIVLAXQS5XCJ4BGM2VEBIXV2 X-Message-ID-Hash: 7QAUNG3GDIVLAXQS5XCJ4BGM2VEBIXV2 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 07/08/2025 08:17, David Gibson wrote: > On Tue, Aug 05, 2025 at 05:46:28PM +0200, Laurent Vivier wrote: >> The packet pool was previously limited to handling packets contained >> within a single buffer. >> >> This patch extends the packet pool to support iovec array, >> allowing a single logical packet to be composed of multiple iovec. >> >> To accommodate this, the storage format within the pool is modified. >> For a multi-vector packet, a header entry is now stored first with >> iov_base = NULL and iov_len holding the number of subsequent >> vectors. The actual data vectors are then stored in the following >> pool slots. >> >> The packet_add_do() and packet_get_do() functions are updated to >> manage this new format for storing and retrieving packets. The >> pool_full() check is also adjusted to ensure there is enough >> space for all vectors of a new packet before adding it. >> >> Signed-off-by: Laurent Vivier >> --- >> packet.c | 50 +++++++++++++++++++++++++++++++++----------------- >> packet.h | 2 +- >> tap.c | 4 ++-- >> 3 files changed, 36 insertions(+), 20 deletions(-) >> >> diff --git a/packet.c b/packet.c >> index 4b93688509a4..d697232d951a 100644 >> --- a/packet.c >> +++ b/packet.c >> @@ -90,12 +90,13 @@ static int packet_check_range(const struct pool *p, const char *ptr, size_t len, >> /** >> * pool_full() - Is a packet pool full? >> * @p: Pointer to packet pool >> + * @data: check data can fit in the pool >> * >> - * Return: true if the pool is full, false if more packets can be added >> + * Return: true if the pool is full, false if data can be added >> */ >> -bool pool_full(const struct pool *p) >> +bool pool_full(const struct pool *p, const struct iov_tail *data) > > Given the slightly changed semantics, I wonder if 'pool_can_fit()' > might be a better name now. okay > >> { >> - return p->count >= p->size; >> + return p->count + data->cnt + (data->cnt > 1) >= p->size; > > This test is only correct if data is already pruned. As I've said > elsewhere, it might be worth changing to the assumption that iov_tails > are pruned everywhere outside the iov_tail internal handling. > > Oh.. also I think the new check is off by one (in the relatively safe > direction). It will say there's no room when there is just exactly > enough room. Could you explain why you think it's off by 1? > >> } >> >> /** >> @@ -108,11 +109,9 @@ bool pool_full(const struct pool *p) >> void packet_add_do(struct pool *p, struct iov_tail *data, >> const char *func, int line) >> { >> - size_t idx = p->count; >> - const char *start; >> - size_t len; >> + size_t idx = p->count, i, offset; >> >> - if (pool_full(p)) { >> + if (pool_full(p, data)) { >> debug("add packet index %zu to pool with size %zu, %s:%i", >> idx, p->size, func, line); >> return; >> @@ -121,18 +120,30 @@ void packet_add_do(struct pool *p, struct iov_tail *data, >> if (!iov_tail_prune(data)) >> return; >> >> - ASSERT(data->cnt == 1); /* we don't support iovec */ >> + if (data->cnt > 1) { >> + p->pkt[idx].iov_base = NULL; >> + p->pkt[idx].iov_len = data->cnt; >> + idx++; >> + } >> >> - len = data->iov[0].iov_len - data->off; >> - start = (char *)data->iov[0].iov_base + data->off; >> + offset = data->off; >> + for (i = 0; i < data->cnt; i++) { >> + const char *start; >> + size_t len; >> >> - if (packet_check_range(p, start, len, func, line)) >> - return; >> + len = data->iov[i].iov_len - offset; >> + start = (char *)data->iov[i].iov_base + offset; >> + offset = 0; >> >> - p->pkt[idx].iov_base = (void *)start; >> - p->pkt[idx].iov_len = len; >> + if (packet_check_range(p, start, len, func, line)) >> + return; >> >> - p->count++; >> + p->pkt[idx].iov_base = (void *)start; >> + p->pkt[idx].iov_len = len; >> + idx++; > > Hm. Isn't the above equivalent to iov_tail_clone()? Is calling > packet_check_range() on each chunk the only reason for open-coding it > here? Yes, I think the code is clearer like this. And it avoids to scan the iovec array twice (with the offset management). Thanks, Laurent