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([2401:4900:1c7e:7fd6:5c7b:30a9:c6b6:f81d]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2291eedea62sm9093665ad.55.2025.03.27.22.09.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 27 Mar 2025 22:09:48 -0700 (PDT) Message-ID: Date: Fri, 28 Mar 2025 10:39:43 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC v5 3/7] vhost: Forward descriptors to device via packed SVQ To: Eugenio Perez Martin Cc: sgarzare@redhat.com, mst@redhat.com, qemu-devel@nongnu.org, sahilcdq@proton.me References: <20250324135929.74945-1-sahilcdq@proton.me> <20250324135929.74945-4-sahilcdq@proton.me> Content-Language: en-US From: Sahil Siddiq Autocrypt: addr=icegambit91@gmail.com; keydata= xsDNBGcgaYEBDADpKUSKbchLCMdCuZGkuF50/7BiraKc8Ch+mk4T+2+E2/6qXAkalvCkFoqx 3/sa35rconZAFzB/r19e7i3UajIQjATvENrGxqe/IFqcJxo2Jr1HQBwCrsmlQoUCilSC6nDi ejcEIAFytJORDkCcZwLXPjdf5/4pbqVAW5823LB5j5F0TqHAnGY1RhS2V1eBPdRqjAA3xecT zTmLHlkqAXgM2DOot1KbycedZSieCwEykTXMaLC0/3Gyo2Cp1WTWOIyD0hsXpLyFioV4FaX2 Lm+z45Zc4PoNXeC6+l4PdDxixs+saAbadknP+9omwlb+PkMd3esq2wkowTwTJVJK8FCCNTo5 2OArA/ddxcyXY25JHN7vzGooFNW6Bb9YV+lbX6y95ytE3KcAmid73tQrcjlebIpgNAvOMyyZ BgQJY0HSu3DGNZuKtbNM3iTl82TFj7MVgkEffgF83N6XyBqDztIz2lN47/q5wyRi3jda9NDt geI+Nv145HjulO7bI3NT048AEQEAAc0kU2FoaWwgU2lkZGlxIDxpY2VnYW1iaXQ5MUBnbWFp bC5jb20+wsENBBMBCAA3FiEERtYfQYWFu+uAZjYrrzGlXdb6f1cFAmcgaYEFCQWjmoACGwME CwkIBwUVCAkKCwUWAgMBAAAKCRCvMaVd1vp/V/nnC/9KnNIr4a3JW3E/snxv1+XIyUmHBDLn PKBmLDYxO9RJe1xKo/sNmLEno4c8G1F/y12TLV086cpBYGKkE8mPMBABqxuiPG8srwoKc2HW bvoC2Zfeu/WeQ0YqeI9ZEwRhsDGQZ7vc8PnKnEUaPZn6iWW4GeX7dXWeGNrK0wU2B04l2d+M FIKaoPHk8w5Ff++QNcn0YRkm//nYlukHUrMxhNcuc18jaLLftOh7BH/4EbKtTN75KAFePQBi I2CbuC41fchTt12QrPB3yz1GKfudsEMLFHBNeComJNnuolPOq0YSyuKdRO8Jubn5ZqWQeTwj XbG7wTonDc8xe46irOhz36VcjsjSY+PYhVZSeDWeDUZgpaJkBjQDDodIN2eoMwVEyUByos9H mKrqrpBMmylOspAZzqjb5FtOqM0BCxQINdKKiMwRelSb6pHYCrbS0XzpwDUEpp7RWCbHgg+6 Ot72kQCEFxj2LzX9VxF24GGQy9inlUfN51IV04klSibtBuuz/NbOwM0EZyBpgQEMAJelVX4k CtCxD4Ji3FQ8LZs22z7VoUvqIb7Gj2lNvhPeijlqqBkSMIgnSCLxlH4ahqKnEV58IrfVriV0 92zb94Az2nl0r+bZYfvev1qCcVIYxk+pYYcRl5qPXX8XGalrkcBBWmkgTSwzNK9rV4850iVI hsJNel49qen9JwiFYMSKa2MYgdYSbeuuwXwUp0ZHeVFc5RnPK2wxws1xcnsdb9hRXs2UeTEE 0klG3HuXqJ96DzKrCieKHLjs330h+16gDWAFZSEoT7Mh3HFGI2dscVuBstQNgnwUMnsJv8jx c005CfLCjCBnJEhMd2/QFuLwCZv4IdoghKwYw18e61UbX2bFovo9dduD527pD4sFqi7U7ofv aO3yf+ulL6jiKypGvnbiBP3KY3aKxx6pHHH3aDc9eOqCUgrtS3+xt1du4+qxrYqEnrywFoJy 5zqSzbnTTjFpdTbY5SS52fIOktLlAKzEg6V9hkg2r08hC3/L4NVj6I4tsGZlqb2neRlHFmCr bQARAQABwsD8BBgBCAAmFiEERtYfQYWFu+uAZjYrrzGlXdb6f1cFAmcgaYIFCQWjmoACGwwA CgkQrzGlXdb6f1fDIgwAmpB7eL3XNSx3F+gbmksOPMqCU5rEswRedjEt6tBzFTXhdNFfhZTb vCddUNePZnzddgxAnDBcTqI1jx6Go6Hkti/mxJqXSczMYBsImD/lEm47axsADvpnNaEM+tmu m/cMKfpILUpy2Ey7CKXUA1vpzYeUD29EQWi0fxM0arplrVt/uzUdFRFQRn2hCqeDLBLONX1F Adq+re6M0dhKl4a2+erzZRIXh3vIGiDmpJEGrajrhqEnMXFp6toSiMGian94m8H3NT6rB64E JmdHgyjXADFbn2G5Mb6Pwa8KnnK1kYcZ+Pwu9LfMXfgI01Sh/k01hjUVmnpYep4nHUfwXA8r kn6WekD80DYbAfKyFAXQCO/nclZ82RNmJbDRi3AeMFrxKi6KgdGCp1Izhj9USaMOVqcuV2p0 Rsoq+sFqWOKaHWnQHCM9RkynQVqrgUaSawEbGlCP1KIhVmjfjVsmsCaKkUb9T6VeO+ZNe+Pn rPgMe6IIvn24UuW2f6fIt0AaqOWq In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::62c; envelope-from=icegambit91@gmail.com; helo=mail-pl1-x62c.google.com X-Spam_score_int: -17 X-Spam_score: -1.8 X-Spam_bar: - X-Spam_report: (-1.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Hi, On 3/26/25 5:32 PM, Eugenio Perez Martin wrote: > On Mon, Mar 24, 2025 at 3:00 PM Sahil Siddiq wrote: >> >> Implement the insertion of available buffers in the descriptor area of >> packed shadow virtqueues. It takes into account descriptor chains, but >> does not consider indirect descriptors. >> >> Enable the packed SVQ to forward the descriptors to the device. >> >> Signed-off-by: Sahil Siddiq >> --- >> Changes from v4 -> v5: >> - This was commit #2 in v4. This has been reordered to commit #3 >> based on review comments. >> - vhost-shadow-virtqueue.c: >> (vhost_svq_valid_features): Move addition of enums to commit #6 >> based on review comments. >> (vhost_svq_add_packed): Set head_idx to buffer id instead of vring's >> index. >> (vhost_svq_kick): Split into vhost_svq_kick_split and >> vhost_svq_kick_packed. >> (vhost_svq_add): Use new vhost_svq_kick_* functions. >> >> hw/virtio/vhost-shadow-virtqueue.c | 117 +++++++++++++++++++++++++++-- >> 1 file changed, 112 insertions(+), 5 deletions(-) >> >> diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c >> index 4f74ad402a..6e16cd4bdf 100644 >> --- a/hw/virtio/vhost-shadow-virtqueue.c >> +++ b/hw/virtio/vhost-shadow-virtqueue.c >> @@ -193,10 +193,83 @@ static void vhost_svq_add_split(VhostShadowVirtqueue *svq, >> /* Update the avail index after write the descriptor */ >> smp_wmb(); >> avail->idx = cpu_to_le16(svq->shadow_avail_idx); >> +} >> + >> +/** >> + * Write descriptors to SVQ packed vring >> + * >> + * @svq: The shadow virtqueue >> + * @out_sg: The iovec to the guest >> + * @out_num: Outgoing iovec length >> + * @in_sg: The iovec from the guest >> + * @in_num: Incoming iovec length >> + * @sgs: Cache for hwaddr >> + * @head: Saves current free_head >> + */ >> +static void vhost_svq_add_packed(VhostShadowVirtqueue *svq, >> + const struct iovec *out_sg, size_t out_num, >> + const struct iovec *in_sg, size_t in_num, >> + hwaddr *sgs, unsigned *head) >> +{ >> + uint16_t id, curr, i, head_flags = 0, head_idx; >> + size_t num = out_num + in_num; >> + unsigned n; >> + >> + struct vring_packed_desc *descs = svq->vring_packed.vring.desc; >> + >> + head_idx = svq->vring_packed.next_avail_idx; >> + i = head_idx; >> + id = svq->free_head; >> + curr = id; >> + *head = id; >> + >> + /* Write descriptors to SVQ packed vring */ >> + for (n = 0; n < num; n++) { >> + uint16_t flags = cpu_to_le16(svq->vring_packed.avail_used_flags | >> + (n < out_num ? 0 : VRING_DESC_F_WRITE) | >> + (n + 1 == num ? 0 : VRING_DESC_F_NEXT)); >> + if (i == head_idx) { >> + head_flags = flags; >> + } else { >> + descs[i].flags = flags; >> + } >> + >> + descs[i].addr = cpu_to_le64(sgs[n]); >> + descs[i].id = id; >> + if (n < out_num) { >> + descs[i].len = cpu_to_le32(out_sg[n].iov_len); >> + } else { >> + descs[i].len = cpu_to_le32(in_sg[n - out_num].iov_len); >> + } >> + >> + curr = cpu_to_le16(svq->desc_next[curr]); >> + >> + if (++i >= svq->vring_packed.vring.num) { >> + i = 0; >> + svq->vring_packed.avail_used_flags ^= >> + 1 << VRING_PACKED_DESC_F_AVAIL | >> + 1 << VRING_PACKED_DESC_F_USED; >> + } >> + } >> >> + if (i <= head_idx) { >> + svq->vring_packed.avail_wrap_counter ^= 1; >> + } >> + >> + svq->vring_packed.next_avail_idx = i; >> + svq->shadow_avail_idx = i; >> + svq->free_head = curr; >> + >> + /* >> + * A driver MUST NOT make the first descriptor in the list >> + * available before all subsequent descriptors comprising >> + * the list are made available. >> + */ >> + smp_wmb(); >> + svq->vring_packed.vring.desc[head_idx].flags = head_flags; >> } >> >> -static void vhost_svq_kick(VhostShadowVirtqueue *svq) >> +static void vhost_svq_kick_split(VhostShadowVirtqueue *svq) >> { >> bool needs_kick; >> >> @@ -209,7 +282,8 @@ static void vhost_svq_kick(VhostShadowVirtqueue *svq) >> if (virtio_vdev_has_feature(svq->vdev, VIRTIO_RING_F_EVENT_IDX)) { >> uint16_t avail_event = le16_to_cpu( >> *(uint16_t *)(&svq->vring.used->ring[svq->vring.num])); >> - needs_kick = vring_need_event(avail_event, svq->shadow_avail_idx, svq->shadow_avail_idx - 1); >> + needs_kick = vring_need_event(avail_event, svq->shadow_avail_idx, >> + svq->shadow_avail_idx - 1); >> } else { >> needs_kick = >> !(svq->vring.used->flags & cpu_to_le16(VRING_USED_F_NO_NOTIFY)); >> @@ -222,6 +296,30 @@ static void vhost_svq_kick(VhostShadowVirtqueue *svq) >> event_notifier_set(&svq->hdev_kick); >> } >> >> +static void vhost_svq_kick_packed(VhostShadowVirtqueue *svq) >> +{ >> + bool needs_kick; >> + >> + /* >> + * We need to expose the available array entries before checking >> + * notification suppressions. >> + */ >> + smp_mb(); >> + >> + if (virtio_vdev_has_feature(svq->vdev, VIRTIO_RING_F_EVENT_IDX)) { >> + return; > > It's weird SVQ does not need to kick if _F_EVENT_IDX. This should have > code checking the device ring flags etc. > Right, I haven't implemented this yet. Since the current implementation is being tested with event_idx=off (points 3 and 4 of the roadmap [1]), I thought I would leave this for later. Maybe I can add a comment in the implementation explaining this. Thanks, Sahil [1] https://wiki.qemu.org/Internships/ProjectIdeas/PackedShadowVirtqueue