From patchwork Tue Jun 2 13:05:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 11583809 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 5C6E2159A for ; Tue, 2 Jun 2020 13:08:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 331DA2074B for ; Tue, 2 Jun 2020 13:08:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ae6c9cdp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728080AbgFBNIk (ORCPT ); Tue, 2 Jun 2020 09:08:40 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:51337 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727794AbgFBNGF (ORCPT ); Tue, 2 Jun 2020 09:06:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591103162; 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; bh=hcgLS8sOOa0jYGy0/GUbI7V052A2CYejMEqoXlLou1w=; b=ae6c9cdp3W4XpaX7jbhTMTJzRt6gT30+MGkuWYXKWwBhDoR64K283Nu0zSjpQut/4KiRUz 8KCAphr0UCjP2Zi3ekGWinrn/7cNxAry8n8sbbchzt9zK2F8rUvkdDHgRR4ozODhx3qxQq NiKOVfp2bDCX/sEOPcObj/UDc/b2ReA= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-495-LCR2CnbROeOkPLJy8oVvkg-1; Tue, 02 Jun 2020 09:06:00 -0400 X-MC-Unique: LCR2CnbROeOkPLJy8oVvkg-1 Received: by mail-wm1-f70.google.com with SMTP id p24so936615wmc.1 for ; Tue, 02 Jun 2020 06:06:00 -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:content-transfer-encoding :in-reply-to; bh=hcgLS8sOOa0jYGy0/GUbI7V052A2CYejMEqoXlLou1w=; b=NTRnalgYJ3lgja5FBLBxDAz222JnuJ19z/+WG6fu/Admux+8/Huoia1pT1EivUS6Dc FFsIVKjcB5+fEDoTF0fTh3jgJwhvdOiJTia4MP52UtArdzwWYxnYwX4w1M9xMwCkTIw8 U72c7rAkKi1VIwPBIx2g+F7JtcOr6AQSo0FaGkqOYqpWJFeKGt2Pr9TgyttvYceDa5Sb tZib1wQBs7oiGvKr+Mnygq5Ru70NU2hbNmF3ZPho0en2kvol/hKw7Xf4FXn0AKr3qHJ/ 19RuWIcLvBAaBzrcZLVXExpq17OQL6SxjL3eIg36DJbxxXW8y++tuVZeE/UpLURiQMu+ N1Vg== X-Gm-Message-State: AOAM531Ib7RTPC8pjM+jglJYzoEEBMYVTO/GG5gN3srdmgdSeZMOqIej bCO0JmEAFJQNA45PQcjVXGIqWBTUHi6q5bL1q19ESUUR4UO0vDX45QXM78382GYLAC9WWCjWqAn VH/tj0hKc+Hlh X-Received: by 2002:a5d:49cd:: with SMTP id t13mr28797873wrs.292.1591103159337; Tue, 02 Jun 2020 06:05:59 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxG95U3Hjq7TfVK36tpHBgrirHTNymuvShxx7I3iWEYYOa9vousA3XZILFVeznxGhe2mvUy/A== X-Received: by 2002:a5d:49cd:: with SMTP id t13mr28797839wrs.292.1591103158927; Tue, 02 Jun 2020 06:05:58 -0700 (PDT) Received: from redhat.com (bzq-109-64-41-91.red.bezeqint.net. [109.64.41.91]) by smtp.gmail.com with ESMTPSA id v2sm3783903wrn.21.2020.06.02.06.05.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Jun 2020 06:05:58 -0700 (PDT) Date: Tue, 2 Jun 2020 09:05:56 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: Eugenio =?utf-8?b?UMOpcmV6?= , Jason Wang , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: [PATCH RFC 01/13] vhost: option to fetch descriptors through an independent struct Message-ID: <20200602130543.578420-2-mst@redhat.com> References: <20200602130543.578420-1-mst@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200602130543.578420-1-mst@redhat.com> X-Mailer: git-send-email 2.24.1.751.gd10ce2899c 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. When used, this causes a minor performance degradation, it's been kept as simple as possible for ease of review. A follow-up patch gets us back the performance by adding batching. To simplify benchmarking, I kept the old code around so one can switch back and forth between old and new code. This will go away in the final submission. Signed-off-by: Michael S. Tsirkin Signed-off-by: Eugenio Pérez Link: https://lore.kernel.org/r/20200401183118.8334-2-eperezma@redhat.com Signed-off-by: Michael S. Tsirkin --- drivers/vhost/vhost.c | 297 +++++++++++++++++++++++++++++++++++++++++- drivers/vhost/vhost.h | 16 +++ 2 files changed, 312 insertions(+), 1 deletion(-) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 96d9871fa0cb..105fc97af2c8 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -298,6 +298,7 @@ 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; @@ -368,6 +369,9 @@ 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); @@ -384,6 +388,10 @@ 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); @@ -391,7 +399,7 @@ 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; @@ -2277,6 +2285,293 @@ 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; +} + +#define VHOST_DESC_FLAGS (VRING_DESC_F_INDIRECT | VRING_DESC_F_WRITE | \ + VRING_DESC_F_NEXT) +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) & VHOST_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) +{ + unsigned int i, head, found = 0; + struct vhost_desc *last; + struct vring_desc desc; + __virtio16 avail_idx; + __virtio16 ring_head; + u16 last_avail_idx; + 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); + + last = peek_split_desc(vq); + if (unlikely(last->flags & VRING_DESC_F_INDIRECT)) { + pop_split_desc(vq); + ret = fetch_indirect_descs(vq, last, head); + if (unlikely(ret < 0)) { + if (ret != -EAGAIN) + vq_err(vq, "Failure detected " + "in indirect descriptor at idx %d\n", head); + return ret; + } + } + + /* 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)); + + /* On success, increment avail index. */ + vq->last_avail_idx++; + + 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); + int i; + + if (ret) + 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 & ~VHOST_DESC_FLAGS) { + 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 = desc->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 60cab4c78229..0976a2853935 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -60,6 +60,13 @@ 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; @@ -71,6 +78,11 @@ struct vhost_virtqueue { vring_avail_t __user *avail; vring_used_t __user *used; const struct vhost_iotlb_map *meta_iotlb[VHOST_NUM_ADDRS]; + + struct vhost_desc *descs; + int ndescs; + int max_descs; + struct file *kick; struct eventfd_ctx *call_ctx; struct eventfd_ctx *error_ctx; @@ -175,6 +187,10 @@ 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,