Re: [RFC v4 3/3] vhost: introduce mdev based hardware backend
From: Jason Wang
Date: Tue Sep 17 2019 - 03:26:52 EST
On 2019/9/17 äå9:02, Tiwei Bie wrote:
More details about this patch can be found from the cover
letter for now. Only compile test has been done for now.
Signed-off-by: Tiwei Bie <tiwei.bie@xxxxxxxxx>
---
drivers/vhost/Kconfig | 9 +
drivers/vhost/Makefile | 3 +
drivers/vhost/mdev.c | 462 +++++++++++++++++++++++++++++++
drivers/vhost/vhost.c | 39 ++-
drivers/vhost/vhost.h | 6 +
include/uapi/linux/vhost.h | 10 +
include/uapi/linux/vhost_types.h | 5 +
7 files changed, 528 insertions(+), 6 deletions(-)
create mode 100644 drivers/vhost/mdev.c
diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index 3d03ccbd1adc..ef9783156d2e 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -34,6 +34,15 @@ config VHOST_VSOCK
To compile this driver as a module, choose M here: the module will be called
vhost_vsock.
+config VHOST_MDEV
+ tristate "Mediated device based hardware vhost accelerator"
+ depends on EVENTFD && VFIO && VFIO_MDEV
+ select VHOST
+ default n
+ ---help---
+ Say Y here to enable the vhost_mdev module
+ for use with hardware vhost accelerators
+
config VHOST
tristate
---help---
diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile
index 6c6df24f770c..ad9c0f8c6d8c 100644
--- a/drivers/vhost/Makefile
+++ b/drivers/vhost/Makefile
@@ -10,4 +10,7 @@ vhost_vsock-y := vsock.o
obj-$(CONFIG_VHOST_RING) += vringh.o
+obj-$(CONFIG_VHOST_MDEV) += vhost_mdev.o
+vhost_mdev-y := mdev.o
+
obj-$(CONFIG_VHOST) += vhost.o
diff --git a/drivers/vhost/mdev.c b/drivers/vhost/mdev.c
new file mode 100644
index 000000000000..8c6597aff45e
--- /dev/null
+++ b/drivers/vhost/mdev.c
@@ -0,0 +1,462 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018-2019 Intel Corporation.
+ */
+
+#include <linux/compat.h>
+#include <linux/kernel.h>
+#include <linux/miscdevice.h>
+#include <linux/mdev.h>
+#include <linux/module.h>
+#include <linux/vfio.h>
+#include <linux/vhost.h>
+#include <linux/virtio_mdev.h>
+
+#include "vhost.h"
+
+struct vhost_mdev {
+ struct mutex mutex;
+ struct vhost_dev dev;
+ struct vhost_virtqueue *vqs;
+ int nvqs;
+ u64 state;
+ u64 features;
+ u64 acked_features;
+ struct vfio_group *vfio_group;
+ struct vfio_device *vfio_device;
+ struct mdev_device *mdev;
+};
+
+/*
+ * XXX
+ * We assume virtio_mdev.ko exposes below symbols for now, as we
+ * don't have a proper way to access parent ops directly yet.
+ *
+ * virtio_mdev_readl()
+ * virtio_mdev_writel()
+ */
+extern u32 virtio_mdev_readl(struct mdev_device *mdev, loff_t off);
+extern void virtio_mdev_writel(struct mdev_device *mdev, loff_t off, u32 val);
Need to consider a better approach, I feel we should do it through some
kind of mdev driver instead of talk to mdev device directly.
+
+static u8 mdev_get_status(struct mdev_device *mdev)
+{
+ return virtio_mdev_readl(mdev, VIRTIO_MDEV_STATUS);
+}
+
+static void mdev_set_status(struct mdev_device *mdev, u8 status)
+{
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_STATUS, status);
+}
+
+static void mdev_add_status(struct mdev_device *mdev, u8 status)
+{
+ status |= mdev_get_status(mdev);
+ mdev_set_status(mdev, status);
+}
+
+static void mdev_reset(struct mdev_device *mdev)
+{
+ mdev_set_status(mdev, 0);
+}
+
+static void handle_vq_kick(struct vhost_work *work)
+{
+ struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
+ poll.work);
+ struct vhost_mdev *m = container_of(vq->dev, struct vhost_mdev, dev);
+
+ virtio_mdev_writel(m->mdev, VIRTIO_MDEV_QUEUE_NOTIFY, vq - m->vqs);
+}
+
+static long vhost_mdev_start_backend(struct vhost_mdev *m)
+{
+ struct mdev_device *mdev = m->mdev;
+ u64 features = m->acked_features;
+ u64 addr;
+ struct vhost_virtqueue *vq;
+ int queue_id;
+
+ features |= 1ULL << VIRTIO_F_IOMMU_PLATFORM;
Is it better to get this feature from backend?
+
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_DRIVER_FEATURES_SEL, 1);
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_DRIVER_FEATURES,
+ (u32)(features >> 32));
+
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_DRIVER_FEATURES_SEL, 0);
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_DRIVER_FEATURES,
+ (u32)features);
+
+ mdev_add_status(mdev, VIRTIO_CONFIG_S_FEATURES_OK);
+ if (!(mdev_get_status(mdev) & VIRTIO_CONFIG_S_FEATURES_OK))
+ return -ENODEV;
+
+ for (queue_id = 0; queue_id < m->nvqs; queue_id++) {
+ vq = &m->vqs[queue_id];
+
+ if (!vq->desc || !vq->avail || !vq->used)
+ break;
+
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_QUEUE_NUM, vq->num);
+
+ if (!vhost_translate_ring_addr(vq, (u64)vq->desc,
+ vhost_get_desc_size(vq, vq->num),
+ &addr))
+ return -EINVAL;
Interesting, any reason for doing such kinds of translation to HVA? I
believe the add should already an IOVA that has been map by VFIO.
+
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_QUEUE_DESC_LOW, addr);
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_QUEUE_DESC_HIGH,
+ (addr >> 32));
+
+ if (!vhost_translate_ring_addr(vq, (u64)vq->avail,
+ vhost_get_avail_size(vq, vq->num),
+ &addr))
+ return -EINVAL;
+
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_QUEUE_AVAIL_LOW, addr);
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_QUEUE_AVAIL_HIGH,
+ (addr >> 32));
+
+ if (!vhost_translate_ring_addr(vq, (u64)vq->used,
+ vhost_get_used_size(vq, vq->num),
+ &addr))
+ return -EINVAL;
+
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_QUEUE_USED_LOW, addr);
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_QUEUE_USED_HIGH,
+ (addr >> 32));
+
+ // XXX: we need to support set_vring_base
I'm working on V2 that support this API.
+
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_QUEUE_READY, 1);
+ }
+
+ // XXX: we need to setup interrupt as well
V2 will have a better interrupt API like some kind of callback. It could
be as simple as a wrapper of eventfd_signal().
+
+ mdev_add_status(mdev, VIRTIO_CONFIG_S_DRIVER_OK);
+ return 0;
+}
+
+static long vhost_mdev_stop_backend(struct vhost_mdev *m)
+{
+ struct mdev_device *mdev = m->mdev;
+
+ mdev_reset(mdev);
+ mdev_add_status(mdev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
+ mdev_add_status(mdev, VIRTIO_CONFIG_S_DRIVER);
+ return 0;
+}
+
+static long vhost_set_state(struct vhost_mdev *m, u64 __user *statep)
+{
+ u64 state;
+ long r;
+
+ if (copy_from_user(&state, statep, sizeof(state)))
+ return -EFAULT;
+
+ if (state >= VHOST_MDEV_S_MAX)
+ return -EINVAL;
+
+ if (m->state == state)
+ return 0;
+
+ m->state = state;
+
+ switch (m->state) {
+ case VHOST_MDEV_S_RUNNING:
+ r = vhost_mdev_start_backend(m);
+ break;
+ case VHOST_MDEV_S_STOPPED:
+ r = vhost_mdev_stop_backend(m);
+ break;
+ default:
+ r = -EINVAL;
+ break;
+ }
+
+ return r;
+}
+
+static long vhost_get_features(struct vhost_mdev *m, u64 __user *featurep)
+{
+ if (copy_to_user(featurep, &m->features, sizeof(m->features)))
+ return -EFAULT;
+ return 0;
+}
+
+static long vhost_set_features(struct vhost_mdev *m, u64 __user *featurep)
+{
+ u64 features;
+
+ if (copy_from_user(&features, featurep, sizeof(features)))
+ return -EFAULT;
+
+ if (features & ~m->features)
+ return -EINVAL;
+
+ m->acked_features = features;
+
+ return 0;
+}
+
+static long vhost_get_vring_base(struct vhost_mdev *m, void __user *argp)
+{
+ struct vhost_virtqueue *vq;
+ u32 idx;
+ long r;
+
+ r = get_user(idx, (u32 __user *)argp);
+ if (r < 0)
+ return r;
+ if (idx >= m->nvqs)
+ return -ENOBUFS;
+
+ vq = &m->vqs[idx];
+
+ // XXX: we need to support get_vring_base
+ //vq->last_avail_idx = virtio_mdev_readl(b->mdev, ...);
+
+ return vhost_vring_ioctl(&m->dev, VHOST_GET_VRING_BASE, argp);
+}
+
+static void vhost_mdev_release_backend(struct vhost_mdev *m)
+{
+ if (!m->mdev)
+ return;
+
+ if (m->state != VHOST_MDEV_S_STOPPED) {
+ m->state = VHOST_MDEV_S_STOPPED;
+ vhost_mdev_stop_backend(m);
+ }
+
+ vhost_dev_stop(&m->dev);
+ vhost_dev_cleanup(&m->dev);
+
+ kfree(m->dev.vqs);
+ kfree(m->vqs);
+
+ vfio_device_put(m->vfio_device);
+ vfio_group_put_external_user(m->vfio_group);
+
+ m->mdev = NULL;
+}
+
+static long vhost_mdev_set_backend(struct vhost_mdev *m,
+ struct vhost_mdev_backend __user *argp)
+{
+ struct vhost_mdev_backend backend;
+ struct mdev_device *mdev;
+ struct vhost_dev *dev;
+ struct vhost_virtqueue **vqs;
+ struct file *file;
+ struct vfio_device *device;
+ struct vfio_group *group;
+ unsigned long magic;
+ u64 features;
+ int i, nvqs;
+ long r;
+
+ vhost_mdev_release_backend(m);
+
+ if (copy_from_user(&backend, argp, sizeof(backend))) {
+ r = -EFAULT;
+ goto err;
+ }
+
+ file = fget(backend.group_fd);
+ if (!file) {
+ r = -EBADF;
+ goto err;
+ }
+
+ group = vfio_group_get_external_user(file);
+ fput(file);
+ if (IS_ERR(group)) {
+ r = PTR_ERR(group);
+ goto err;
+ }
+
+ device = vfio_device_get_from_fd(group, backend.device_fd);
+ if (!IS_ERR(device)) {
+ r = PTR_ERR(device);
+ goto err_put_group;
+ }
+
+ if (!vfio_device_ops_match(device, &vfio_mdev_dev_ops)) {
+ r = -EINVAL;
+ goto err_put_device;
+ }
It looks to me that we can avoid to expose vfio_mdev_dev_ops here.
+
+ mdev = vfio_device_data(m->vfio_device);
+
+ magic = virtio_mdev_readl(mdev, VIRTIO_MDEV_MAGIC_VALUE);
+ if (magic != ('v' | 'i' << 8 | 'r' << 16 | 't' << 24)) {
+ r = -ENODEV;
+ goto err_put_device;
+ }
+
+ mdev_reset(mdev);
+ mdev_add_status(mdev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
+ mdev_add_status(mdev, VIRTIO_CONFIG_S_DRIVER);
+
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_DEVICE_FEATURES_SEL, 1);
+ features = virtio_mdev_readl(mdev, VIRTIO_MDEV_DEVICE_FEATURES);
+ features <<= 32;
+
+ virtio_mdev_writel(mdev, VIRTIO_MDEV_DEVICE_FEATURES_SEL, 0);
+ features |= virtio_mdev_readl(mdev, VIRTIO_MDEV_DEVICE_FEATURES);
+
+ if (!(features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))) {
+ r = -EINVAL;
+ goto err_put_device;
+ }
+
+ m->features = features;
+
+ nvqs = virtio_mdev_readl(mdev, VIRTIO_MDEV_QUEUE_NUM_MAX);
+ m->nvqs = nvqs;
+
+ m->vqs = kmalloc_array(nvqs, sizeof(struct vhost_virtqueue),
+ GFP_KERNEL);
+ if (!m->vqs) {
+ r = -ENOMEM;
+ goto err_put_device;
+ }
+
+ vqs = kmalloc_array(nvqs, sizeof(*vqs), GFP_KERNEL);
+ if (!vqs) {
+ r = -ENOMEM;
+ goto err_free_vqs;
+ }
+
+ dev = &m->dev;
+ for (i = 0; i < nvqs; i++) {
+ vqs[i] = &m->vqs[i];
+ vqs[i]->handle_kick = handle_vq_kick;
+ }
+ vhost_dev_init(dev, vqs, nvqs, 0, 0, 0);
+
+ m->vfio_group = group;
+ m->vfio_device = device;
+ m->mdev = mdev;
+
+ return 0;
+
+err_free_vqs:
+ kfree(m->vqs);
+err_put_device:
+ vfio_device_put(device);
+err_put_group:
+ vfio_group_put_external_user(group);
+err:
+ return r;
+}
+
+static int vhost_mdev_open(struct inode *inode, struct file *f)
+{
+ struct vhost_mdev *m;
+
+ m = kzalloc(sizeof(*m), GFP_KERNEL | __GFP_RETRY_MAYFAIL);
+ if (!m)
+ return -ENOMEM;
+
+ mutex_init(&m->mutex);
+ f->private_data = m;
+
+ return 0;
+}
+
+static int vhost_mdev_release(struct inode *inode, struct file *f)
+{
+ struct vhost_mdev *m = f->private_data;
+
+ vhost_mdev_release_backend(m);
+ mutex_destroy(&m->mutex);
+ kfree(m);
+
+ return 0;
+}
+
+static long vhost_mdev_ioctl(struct file *f, unsigned int cmd,
+ unsigned long arg)
+{
+ void __user *argp = (void __user *)arg;
+ struct vhost_mdev *m = f->private_data;
+ long r;
+
+ mutex_lock(&m->mutex);
+
+ if (cmd == VHOST_MDEV_SET_BACKEND) {
+ r = vhost_mdev_set_backend(m, argp);
+ goto done;
+ }
+
+ if (!m->mdev) {
+ r = -EINVAL;
+ goto done;
+ }
+
+ switch (cmd) {
+ case VHOST_MDEV_SET_STATE:
+ r = vhost_set_state(m, argp);
+ break;
+ case VHOST_GET_FEATURES:
+ r = vhost_get_features(m, argp);
+ break;
+ case VHOST_SET_FEATURES:
+ r = vhost_set_features(m, argp);
+ break;
+ case VHOST_GET_VRING_BASE:
+ r = vhost_get_vring_base(m, argp);
+ break;
+ default:
+ r = vhost_dev_ioctl(&m->dev, cmd, argp);
+ if (r == -ENOIOCTLCMD)
+ r = vhost_vring_ioctl(&m->dev, cmd, argp);
+ }
+
+done:
+ mutex_lock(&m->mutex);
+ return r;
+}
+
+#ifdef CONFIG_COMPAT
+static long vhost_mdev_compat_ioctl(struct file *f, unsigned int ioctl,
+ unsigned long arg)
+{
+ return vhost_mdev_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
+}
+#endif
+
+static const struct file_operations vhost_mdev_fops = {
+ .owner = THIS_MODULE,
+ .release = vhost_mdev_release,
+ .unlocked_ioctl = vhost_mdev_ioctl,
+#ifdef CONFIG_COMPAT
+ .compat_ioctl = vhost_mdev_compat_ioctl,
+#endif
+ .open = vhost_mdev_open,
+ .llseek = noop_llseek,
+};
+
+static struct miscdevice vhost_mdev_misc = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "vhost-mdev",
+ .fops = &vhost_mdev_fops,
+};
+
+static int __init vhost_mdev_init(void)
+{
+ return misc_register(&vhost_mdev_misc);
+}
+module_init(vhost_mdev_init);
+
+static void __exit vhost_mdev_exit(void)
+{
+ misc_deregister(&vhost_mdev_misc);
+}
+module_exit(vhost_mdev_exit);
+
+MODULE_VERSION("0.0.0");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Hardware vhost accelerator abstraction");
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 5dc174ac8cac..0f7236a17a56 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -426,8 +426,7 @@ bool vhost_exceeds_weight(struct vhost_virtqueue *vq,
}
EXPORT_SYMBOL_GPL(vhost_exceeds_weight);
-static size_t vhost_get_avail_size(struct vhost_virtqueue *vq,
- unsigned int num)
+size_t vhost_get_avail_size(struct vhost_virtqueue *vq, unsigned int num)
{
size_t event __maybe_unused =
vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
@@ -435,9 +434,9 @@ static size_t vhost_get_avail_size(struct vhost_virtqueue *vq,
return sizeof(*vq->avail) +
sizeof(*vq->avail->ring) * num + event;
}
+EXPORT_SYMBOL_GPL(vhost_get_avail_size);
-static size_t vhost_get_used_size(struct vhost_virtqueue *vq,
- unsigned int num)
+size_t vhost_get_used_size(struct vhost_virtqueue *vq, unsigned int num)
{
size_t event __maybe_unused =
vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
@@ -445,12 +444,13 @@ static size_t vhost_get_used_size(struct vhost_virtqueue *vq,
return sizeof(*vq->used) +
sizeof(*vq->used->ring) * num + event;
}
+EXPORT_SYMBOL_GPL(vhost_get_used_size);
-static size_t vhost_get_desc_size(struct vhost_virtqueue *vq,
- unsigned int num)
+size_t vhost_get_desc_size(struct vhost_virtqueue *vq, unsigned int num)
{
return sizeof(*vq->desc) * num;
}
+EXPORT_SYMBOL_GPL(vhost_get_desc_size);
void vhost_dev_init(struct vhost_dev *dev,
struct vhost_virtqueue **vqs, int nvqs,
@@ -2617,6 +2617,33 @@ struct vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev,
}
EXPORT_SYMBOL_GPL(vhost_dequeue_msg);
+bool vhost_translate_ring_addr(struct vhost_virtqueue *vq, u64 ring_addr,
+ u64 len, u64 *addr)
+{
+ struct vhost_umem *umem = vq->umem;
+ struct vhost_umem_node *u;
+
+ if (vhost_overflow(ring_addr, len))
+ return false;
+
+ if (vq->iotlb) {
+ /* Ring address is already IOVA */
+ *addr = ring_addr;
+ return true;
+ }
+
+ /* Ring address is host virtual address. */
+ list_for_each_entry(u, &umem->umem_list, link) {
+ if (u->userspace_addr <= ring_addr &&
+ u->userspace_addr + u->size >= ring_addr + len) {
+ *addr = ring_addr - u->userspace_addr + u->start;
+ return true;
+ }
+ }
+
+ return false;
+}
+EXPORT_SYMBOL_GPL(vhost_translate_ring_addr);
As we've discussed, this is necessary.
Thanks
static int __init vhost_init(void)
{
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index e9ed2722b633..294a6bcb6adf 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -189,6 +189,12 @@ long vhost_dev_ioctl(struct vhost_dev *, unsigned int ioctl, void __user *argp);
long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp);
bool vhost_vq_access_ok(struct vhost_virtqueue *vq);
bool vhost_log_access_ok(struct vhost_dev *);
+bool vhost_translate_ring_addr(struct vhost_virtqueue *vq, u64 ring_addr,
+ u64 len, u64 *addr);
+
+size_t vhost_get_avail_size(struct vhost_virtqueue *vq, unsigned int num);
+size_t vhost_get_used_size(struct vhost_virtqueue *vq, unsigned int num);
+size_t vhost_get_desc_size(struct vhost_virtqueue *vq, unsigned int num);
int vhost_get_vq_desc(struct vhost_virtqueue *,
struct iovec iov[], unsigned int iov_count,
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index 40d028eed645..7213aedc8506 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -116,4 +116,14 @@
#define VHOST_VSOCK_SET_GUEST_CID _IOW(VHOST_VIRTIO, 0x60, __u64)
#define VHOST_VSOCK_SET_RUNNING _IOW(VHOST_VIRTIO, 0x61, int)
+/* VHOST_MDEV specific defines */
+
+#define VHOST_MDEV_SET_BACKEND _IOW(VHOST_VIRTIO, 0x70, \
+ struct vhost_mdev_backend)
+#define VHOST_MDEV_SET_STATE _IOW(VHOST_VIRTIO, 0x71, __u64)
+
+#define VHOST_MDEV_S_STOPPED 0
+#define VHOST_MDEV_S_RUNNING 1
+#define VHOST_MDEV_S_MAX 2
+
#endif
diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
index c907290ff065..f06f0dbb7e51 100644
--- a/include/uapi/linux/vhost_types.h
+++ b/include/uapi/linux/vhost_types.h
@@ -119,6 +119,11 @@ struct vhost_scsi_target {
unsigned short reserved;
};
+struct vhost_mdev_backend {
+ int group_fd;
+ int device_fd;
+};
+
/* Feature bits */
/* Log all write descriptors. Can be changed while device is active. */
#define VHOST_F_LOG_ALL 26