From patchwork Sat Oct 12 19:18:50 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 11186947 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0A214912 for ; Sat, 12 Oct 2019 19:19:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D5EA220679 for ; Sat, 12 Oct 2019 19:19:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729821AbfJLTS5 (ORCPT ); Sat, 12 Oct 2019 15:18:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51930 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729692AbfJLTS5 (ORCPT ); Sat, 12 Oct 2019 15:18:57 -0400 Received: from mail-qk1-f199.google.com (mail-qk1-f199.google.com [209.85.222.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8B55D356C9 for ; Sat, 12 Oct 2019 19:18:56 +0000 (UTC) Received: by mail-qk1-f199.google.com with SMTP id d25so12623667qkk.17 for ; Sat, 12 Oct 2019 12:18:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=4QQJmzFzcB+s98hCdlFYskwk8yd9+Vjxg/V7InxbF+w=; b=uljssza9GX7QPcQo/NuuoScVRhc2mbb4LubG854qR4xwlz6pu7H1B5yGwpSKXvdlPA DvN7DMuGWis7LgcYYEgxqZP8jnVqNDmcXbmlR3Bqo4ZFcA5P3JtZPoIyV/5aVl4tUhlV Xr0Cx+wHS5zNc5j8Nb9MOkgil4zgpj7z0YMiE56EcKLsNHXMl//1p1lAgDQzRAEz/KPv dv9kLfAsPPoFgTPVnHA0o9JzTdCL+S9KsXHD24FX460din7z1+1xdIg342TsfBCBNQ8/ 8GKV6EmTPAN8/MQskZbGTcq0mwQ83nFlLJ2X5yoXx8+4CNLPi8KjvYCvKtG0VeYpxGNX boTA== X-Gm-Message-State: APjAAAUYMwXExs0b4hiTPRXh0CKr1tEsJHQehFOSOVOvQfvgFjGHN4oo 7xL5wdRAjiNABUXdE5XXEo4ysUYx6VD+mQpoigoD6wtW8E7pA4Brys0iu0BJlvvYD7oln5hM5+e NysSYRULC3AoI X-Received: by 2002:a37:65d0:: with SMTP id z199mr21529265qkb.137.1570907935585; Sat, 12 Oct 2019 12:18:55 -0700 (PDT) X-Google-Smtp-Source: APXvYqyT3x3y3mOqhW8zjIYMgyV4Tol+AlDLxT1x66xi6of9QPBAN/ULOCUHzVcDrEbHD57K0CnyUw== X-Received: by 2002:a37:65d0:: with SMTP id z199mr21529232qkb.137.1570907934970; Sat, 12 Oct 2019 12:18:54 -0700 (PDT) Received: from redhat.com (bzq-79-176-10-77.red.bezeqint.net. [79.176.10.77]) by smtp.gmail.com with ESMTPSA id w45sm7611219qtb.47.2019.10.12.12.18.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 12 Oct 2019 12:18:54 -0700 (PDT) Date: Sat, 12 Oct 2019 15:18:50 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, Jason Wang Subject: [PATCH RFC v2 1/2] vhost: option to fetch descriptors through an independent struct Message-ID: <20191012191820.8050-2-mst@redhat.com> References: <20191012191820.8050-1-mst@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191012191820.8050-1-mst@redhat.com> X-Mailer: git-send-email 2.22.0.678.g13338e74b8 X-Mutt-Fcc: =sent Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org The idea is to support multiple ring formats by converting to a format-independent array of descriptors. This costs extra cycles, but we gain in ability to fetch a batch of descriptors in one go, which is good for code cache locality. To simplify benchmarking, I kept the old code around so one can switch back and forth by writing into a module parameter. This will go away in the final submission. This patch causes a minor performance degradation, it's been kept as simple as possible for ease of review. Next patch gets us back the performance by adding batching. Signed-off-by: Michael S. Tsirkin --- drivers/vhost/test.c | 17 ++- drivers/vhost/vhost.c | 299 +++++++++++++++++++++++++++++++++++++++++- drivers/vhost/vhost.h | 16 +++ 3 files changed, 327 insertions(+), 5 deletions(-) diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c index 056308008288..39a018a7af2d 100644 --- a/drivers/vhost/test.c +++ b/drivers/vhost/test.c @@ -18,6 +18,9 @@ #include "test.h" #include "vhost.h" +static int newcode = 0; +module_param(newcode, int, 0644); + /* Max number of bytes transferred before requeueing the job. * Using this limit prevents one virtqueue from starving others. */ #define VHOST_TEST_WEIGHT 0x80000 @@ -58,10 +61,16 @@ static void handle_vq(struct vhost_test *n) vhost_disable_notify(&n->dev, vq); for (;;) { - head = vhost_get_vq_desc(vq, vq->iov, - ARRAY_SIZE(vq->iov), - &out, &in, - NULL, NULL); + if (newcode) + head = vhost_get_vq_desc_batch(vq, vq->iov, + ARRAY_SIZE(vq->iov), + &out, &in, + NULL, NULL); + else + head = vhost_get_vq_desc(vq, vq->iov, + ARRAY_SIZE(vq->iov), + &out, &in, + NULL, NULL); /* On error, stop handling until the next kick. */ if (unlikely(head < 0)) break; diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 36ca2cf419bf..36661d6cb51f 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -301,6 +301,7 @@ static void vhost_vq_reset(struct vhost_dev *dev, struct vhost_virtqueue *vq) { vq->num = 1; + vq->ndescs = 0; vq->desc = NULL; vq->avail = NULL; vq->used = NULL; @@ -369,6 +370,9 @@ static int vhost_worker(void *data) static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq) { + kfree(vq->descs); + vq->descs = NULL; + vq->max_descs = 0; kfree(vq->indirect); vq->indirect = NULL; kfree(vq->log); @@ -385,6 +389,10 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev) for (i = 0; i < dev->nvqs; ++i) { vq = dev->vqs[i]; + vq->max_descs = dev->iov_limit; + vq->descs = kmalloc_array(vq->max_descs, + sizeof(*vq->descs), + GFP_KERNEL); vq->indirect = kmalloc_array(UIO_MAXIOV, sizeof(*vq->indirect), GFP_KERNEL); @@ -392,7 +400,7 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev) GFP_KERNEL); vq->heads = kmalloc_array(dev->iov_limit, sizeof(*vq->heads), GFP_KERNEL); - if (!vq->indirect || !vq->log || !vq->heads) + if (!vq->indirect || !vq->log || !vq->heads || !vq->descs) goto err_nomem; } return 0; @@ -2346,6 +2354,295 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq, } EXPORT_SYMBOL_GPL(vhost_get_vq_desc); +static struct vhost_desc *peek_split_desc(struct vhost_virtqueue *vq) +{ + BUG_ON(!vq->ndescs); + return &vq->descs[vq->ndescs - 1]; +} + +static void pop_split_desc(struct vhost_virtqueue *vq) +{ + BUG_ON(!vq->ndescs); + --vq->ndescs; +} + +static int push_split_desc(struct vhost_virtqueue *vq, struct vring_desc *desc, u16 id) +{ + struct vhost_desc *h; + + if (unlikely(vq->ndescs >= vq->max_descs)) + return -EINVAL; + h = &vq->descs[vq->ndescs++]; + h->addr = vhost64_to_cpu(vq, desc->addr); + h->len = vhost32_to_cpu(vq, desc->len); + h->flags = vhost16_to_cpu(vq, desc->flags); + h->id = id; + + return 0; +} + +static int fetch_indirect_descs(struct vhost_virtqueue *vq, + struct vhost_desc *indirect, + u16 head) +{ + struct vring_desc desc; + unsigned int i = 0, count, found = 0; + u32 len = indirect->len; + struct iov_iter from; + int ret; + + /* Sanity check */ + if (unlikely(len % sizeof desc)) { + vq_err(vq, "Invalid length in indirect descriptor: " + "len 0x%llx not multiple of 0x%zx\n", + (unsigned long long)len, + sizeof desc); + return -EINVAL; + } + + ret = translate_desc(vq, indirect->addr, len, vq->indirect, + UIO_MAXIOV, VHOST_ACCESS_RO); + if (unlikely(ret < 0)) { + if (ret != -EAGAIN) + vq_err(vq, "Translation failure %d in indirect.\n", ret); + return ret; + } + iov_iter_init(&from, READ, vq->indirect, ret, len); + + /* We will use the result as an address to read from, so most + * architectures only need a compiler barrier here. */ + read_barrier_depends(); + + count = len / sizeof desc; + /* Buffers are chained via a 16 bit next field, so + * we can have at most 2^16 of these. */ + if (unlikely(count > USHRT_MAX + 1)) { + vq_err(vq, "Indirect buffer length too big: %d\n", + indirect->len); + return -E2BIG; + } + if (unlikely(vq->ndescs + count > vq->max_descs)) { + vq_err(vq, "Too many indirect + direct descs: %d + %d\n", + vq->ndescs, indirect->len); + return -E2BIG; + } + + do { + if (unlikely(++found > count)) { + vq_err(vq, "Loop detected: last one at %u " + "indirect size %u\n", + i, count); + return -EINVAL; + } + if (unlikely(!copy_from_iter_full(&desc, sizeof(desc), &from))) { + vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n", + i, (size_t)indirect->addr + i * sizeof desc); + return -EINVAL; + } + if (unlikely(desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT))) { + vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n", + i, (size_t)indirect->addr + i * sizeof desc); + return -EINVAL; + } + + push_split_desc(vq, &desc, head); + } while ((i = next_desc(vq, &desc)) != -1); + return 0; +} + +static int fetch_descs(struct vhost_virtqueue *vq) +{ + struct vring_desc desc; + unsigned int i, head, found = 0; + u16 last_avail_idx; + __virtio16 avail_idx; + __virtio16 ring_head; + int ret; + + /* Check it isn't doing very strange things with descriptor numbers. */ + last_avail_idx = vq->last_avail_idx; + + if (vq->avail_idx == vq->last_avail_idx) { + if (unlikely(vhost_get_avail_idx(vq, &avail_idx))) { + vq_err(vq, "Failed to access avail idx at %p\n", + &vq->avail->idx); + return -EFAULT; + } + vq->avail_idx = vhost16_to_cpu(vq, avail_idx); + + if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) { + vq_err(vq, "Guest moved used index from %u to %u", + last_avail_idx, vq->avail_idx); + return -EFAULT; + } + + /* If there's nothing new since last we looked, return + * invalid. + */ + if (vq->avail_idx == last_avail_idx) + return vq->num; + + /* Only get avail ring entries after they have been + * exposed by guest. + */ + smp_rmb(); + } + + /* Grab the next descriptor number they're advertising */ + if (unlikely(vhost_get_avail_head(vq, &ring_head, last_avail_idx))) { + vq_err(vq, "Failed to read head: idx %d address %p\n", + last_avail_idx, + &vq->avail->ring[last_avail_idx % vq->num]); + return -EFAULT; + } + + head = vhost16_to_cpu(vq, ring_head); + + /* If their number is silly, that's an error. */ + if (unlikely(head >= vq->num)) { + vq_err(vq, "Guest says index %u > %u is available", + head, vq->num); + return -EINVAL; + } + + i = head; + do { + if (unlikely(i >= vq->num)) { + vq_err(vq, "Desc index is %u > %u, head = %u", + i, vq->num, head); + return -EINVAL; + } + if (unlikely(++found > vq->num)) { + vq_err(vq, "Loop detected: last one at %u " + "vq size %u head %u\n", + i, vq->num, head); + return -EINVAL; + } + ret = vhost_get_desc(vq, &desc, i); + if (unlikely(ret)) { + vq_err(vq, "Failed to get descriptor: idx %d addr %p\n", + i, vq->desc + i); + return -EFAULT; + } + ret = push_split_desc(vq, &desc, head); + if (unlikely(ret)) { + vq_err(vq, "Failed to save descriptor: idx %d\n", i); + return -EINVAL; + } + } while ((i = next_desc(vq, &desc)) != -1); + + /* On success, increment avail index. */ + vq->last_avail_idx++; + + /* Assume notifications from guest are disabled at this point, + * if they aren't we would need to update avail_event index. */ + BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY)); + + return 0; +} + +/* This looks in the virtqueue and for the first available buffer, and converts + * it to an iovec for convenient access. Since descriptors consist of some + * number of output then some number of input descriptors, it's actually two + * iovecs, but we pack them into one and note how many of each there were. + * + * This function returns the descriptor number found, or vq->num (which is + * never a valid descriptor number) if none was found. A negative code is + * returned on error. */ +int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq, + struct iovec iov[], unsigned int iov_size, + unsigned int *out_num, unsigned int *in_num, + struct vhost_log *log, unsigned int *log_num) +{ + int ret = fetch_descs(vq); + struct vhost_desc *last; + u16 id; + int i; + + if (ret) + return ret; + + last = peek_split_desc(vq); + id = last->id; + + if (last->flags & VRING_DESC_F_INDIRECT) { + int r; + + pop_split_desc(vq); + r = fetch_indirect_descs(vq, last, id); + if (unlikely(r < 0)) { + if (r != -EAGAIN) + vq_err(vq, "Failure detected " + "in indirect descriptor at idx %d\n", id); + return ret; + } + } + + /* Now convert to IOV */ + /* When we start there are none of either input nor output. */ + *out_num = *in_num = 0; + if (unlikely(log)) + *log_num = 0; + + for (i = 0; i < vq->ndescs; ++i) { + unsigned iov_count = *in_num + *out_num; + struct vhost_desc *desc = &vq->descs[i]; + int access; + + if (desc->flags & ~(VRING_DESC_F_INDIRECT | VRING_DESC_F_WRITE)) { + vq_err(vq, "Unexpected flags: 0x%x at descriptor id 0x%x\n", + desc->flags, desc->id); + ret = -EINVAL; + goto err; + } + if (desc->flags & VRING_DESC_F_WRITE) + access = VHOST_ACCESS_WO; + else + access = VHOST_ACCESS_RO; + ret = translate_desc(vq, desc->addr, + desc->len, iov + iov_count, + iov_size - iov_count, access); + if (unlikely(ret < 0)) { + if (ret != -EAGAIN) + vq_err(vq, "Translation failure %d descriptor idx %d\n", + ret, i); + goto err; + } + if (access == VHOST_ACCESS_WO) { + /* If this is an input descriptor, + * increment that count. */ + *in_num += ret; + if (unlikely(log && ret)) { + log[*log_num].addr = desc->addr; + log[*log_num].len = desc->len; + ++*log_num; + } + } else { + /* If it's an output descriptor, they're all supposed + * to come before any input descriptors. */ + if (unlikely(*in_num)) { + vq_err(vq, "Descriptor has out after in: " + "idx %d\n", i); + ret = -EINVAL; + goto err; + } + *out_num += ret; + } + } + + ret = id; + vq->ndescs = 0; + + return ret; + +err: + vhost_discard_vq_desc(vq, 1); + vq->ndescs = 0; + + return ret; +} +EXPORT_SYMBOL_GPL(vhost_get_vq_desc_batch); + /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */ void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n) { diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index e9ed2722b633..1724f61b6c2d 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -80,6 +80,13 @@ enum vhost_uaddr_type { VHOST_NUM_ADDRS = 3, }; +struct vhost_desc { + u64 addr; + u32 len; + u16 flags; /* VRING_DESC_F_WRITE, VRING_DESC_F_NEXT */ + u16 id; +}; + /* The virtqueue structure describes a queue attached to a device. */ struct vhost_virtqueue { struct vhost_dev *dev; @@ -90,6 +97,11 @@ struct vhost_virtqueue { struct vring_desc __user *desc; struct vring_avail __user *avail; struct vring_used __user *used; + + struct vhost_desc *descs; + int ndescs; + int max_descs; + const struct vhost_umem_node *meta_iotlb[VHOST_NUM_ADDRS]; struct file *kick; struct eventfd_ctx *call_ctx; @@ -190,6 +202,10 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg bool vhost_vq_access_ok(struct vhost_virtqueue *vq); bool vhost_log_access_ok(struct vhost_dev *); +int vhost_get_vq_desc_batch(struct vhost_virtqueue *, + struct iovec iov[], unsigned int iov_count, + unsigned int *out_num, unsigned int *in_num, + struct vhost_log *log, unsigned int *log_num); int vhost_get_vq_desc(struct vhost_virtqueue *, struct iovec iov[], unsigned int iov_count, unsigned int *out_num, unsigned int *in_num,