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Subject: Re: [PATCH 4/6] vhost-user: support registering external host notifiers
On Thu, May 24, 2018 at 06:33:34PM +0800, Tiwei Bie wrote:
> This patch introduces VHOST_USER_PROTOCOL_F_HOST_NOTIFIER.
> With this feature negotiated, vhost-user backend can register
> memory region based host notifiers. And it will allow the guest
> driver in the VM to notify the hardware accelerator at the
> vhost-user backend directly.
>
> Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
So maybe we don't need a new VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD?
Let's check VHOST_USER_PROTOCOL_F_HOST_NOTIFIER instead?
> ---
> docs/interop/vhost-user.txt | 33 ++++++++++
> hw/virtio/vhost-user.c | 113 +++++++++++++++++++++++++++++++++
> include/hw/virtio/vhost-user.h | 8 +++
> 3 files changed, 154 insertions(+)
>
> diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
> index 682a683eb4..d51fd58242 100644
> --- a/docs/interop/vhost-user.txt
> +++ b/docs/interop/vhost-user.txt
> @@ -132,6 +132,16 @@ Depending on the request type, payload can be:
> Payload: Size bytes array holding the contents of the virtio
> device's configuration space
>
> + * Vring area description
> + -----------------------
> + | u64 | size | offset |
> + -----------------------
> +
> + u64: a 64-bit integer contains vring index and flags
> + Size: a 64-bit size of this area
> + Offset: a 64-bit offset of this area from the start of the
> + supplied file descriptor
> +
> In QEMU the vhost-user message is implemented with the following struct:
>
> typedef struct VhostUserMsg {
> @@ -146,6 +156,7 @@ typedef struct VhostUserMsg {
> VhostUserLog log;
> struct vhost_iotlb_msg iotlb;
> VhostUserConfig config;
> + VhostUserVringArea area;
> };
> } QEMU_PACKED VhostUserMsg;
>
> @@ -385,6 +396,7 @@ Protocol features
> #define VHOST_USER_PROTOCOL_F_PAGEFAULT 8
> #define VHOST_USER_PROTOCOL_F_CONFIG 9
> #define VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD 10
> +#define VHOST_USER_PROTOCOL_F_HOST_NOTIFIER 11
>
> Master message types
> --------------------
> @@ -782,6 +794,27 @@ Slave message types
> the VHOST_USER_NEED_REPLY flag, master must respond with zero when
> operation is successfully completed, or non-zero otherwise.
>
> + * VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG
> +
> + Id: 3
> + Equivalent ioctl: N/A
> + Slave payload: vring area description
> + Master payload: N/A
> +
> + Sets host notifier for a specified queue. The queue index is contained
> + in the u64 field of the vring area description. The host notifier is
> + described by the file descriptor (typically it's a VFIO device fd) which
> + is passed as ancillary data and the size (which is mmap size and should
> + be the same as host page size) and offset (which is mmap offset) carried
> + in the vring area description. QEMU can mmap the file descriptor based
> + on the size and offset to get a memory range. Registering a host notifier
> + means mapping this memory range to the VM as the specified queue's notify
> + MMIO region. Slave sends this request to tell QEMU to de-register the
> + existing notifier if any and register the new notifier if the request is
> + sent with a file descriptor.
> + This request should be sent only when VHOST_USER_PROTOCOL_F_HOST_NOTIFIER
> + protocol feature has been successfully negotiated.
> +
> VHOST_USER_PROTOCOL_F_REPLY_ACK:
> -------------------------------
> The original vhost-user specification only demands replies for certain
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 70b9610c87..b041343632 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -13,6 +13,7 @@
> #include "hw/virtio/vhost.h"
> #include "hw/virtio/vhost-user.h"
> #include "hw/virtio/vhost-backend.h"
> +#include "hw/virtio/virtio.h"
> #include "hw/virtio/virtio-net.h"
> #include "chardev/char-fe.h"
> #include "sysemu/kvm.h"
> @@ -50,6 +51,7 @@ enum VhostUserProtocolFeature {
> VHOST_USER_PROTOCOL_F_PAGEFAULT = 8,
> VHOST_USER_PROTOCOL_F_CONFIG = 9,
> VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD = 10,
> + VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
> VHOST_USER_PROTOCOL_F_MAX
> };
>
> @@ -94,6 +96,7 @@ typedef enum VhostUserSlaveRequest {
> VHOST_USER_SLAVE_NONE = 0,
> VHOST_USER_SLAVE_IOTLB_MSG = 1,
> VHOST_USER_SLAVE_CONFIG_CHANGE_MSG = 2,
> + VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG = 3,
> VHOST_USER_SLAVE_MAX
> } VhostUserSlaveRequest;
>
> @@ -138,6 +141,12 @@ static VhostUserConfig c __attribute__ ((unused));
> + sizeof(c.size) \
> + sizeof(c.flags))
>
> +typedef struct VhostUserVringArea {
> + uint64_t u64;
> + uint64_t size;
> + uint64_t offset;
> +} VhostUserVringArea;
> +
> typedef struct {
> VhostUserRequest request;
>
> @@ -159,6 +168,7 @@ typedef union {
> struct vhost_iotlb_msg iotlb;
> VhostUserConfig config;
> VhostUserCryptoSession session;
> + VhostUserVringArea area;
> } VhostUserPayload;
>
> typedef struct VhostUserMsg {
> @@ -640,9 +650,37 @@ static int vhost_user_set_vring_num(struct vhost_dev *dev,
> return vhost_set_vring(dev, VHOST_USER_SET_VRING_NUM, ring);
> }
>
> +static void vhost_user_host_notifier_restore(struct vhost_dev *dev,
> + int queue_idx)
> +{
> + struct vhost_user *u = dev->opaque;
> + VhostUserHostNotifier *n = &u->user->notifier[queue_idx];
> + VirtIODevice *vdev = dev->vdev;
> +
> + if (n->addr && !n->set) {
> + virtio_queue_set_host_notifier_mr(vdev, queue_idx, &n->mr, true);
> + n->set = true;
> + }
> +}
> +
> +static void vhost_user_host_notifier_remove(struct vhost_dev *dev,
> + int queue_idx)
> +{
> + struct vhost_user *u = dev->opaque;
> + VhostUserHostNotifier *n = &u->user->notifier[queue_idx];
> + VirtIODevice *vdev = dev->vdev;
> +
> + if (n->addr && n->set) {
> + virtio_queue_set_host_notifier_mr(vdev, queue_idx, &n->mr, false);
> + n->set = false;
> + }
> +}
> +
> static int vhost_user_set_vring_base(struct vhost_dev *dev,
> struct vhost_vring_state *ring)
> {
> + vhost_user_host_notifier_restore(dev, ring->index);
> +
> return vhost_set_vring(dev, VHOST_USER_SET_VRING_BASE, ring);
> }
>
> @@ -676,6 +714,8 @@ static int vhost_user_get_vring_base(struct vhost_dev *dev,
> .hdr.size = sizeof(msg.payload.state),
> };
>
> + vhost_user_host_notifier_remove(dev, ring->index);
> +
> if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> return -1;
> }
> @@ -849,6 +889,66 @@ static int vhost_user_slave_handle_config_change(struct vhost_dev *dev)
> return ret;
> }
>
> +static int vhost_user_slave_handle_vring_host_notifier(struct vhost_dev *dev,
> + VhostUserVringArea *area,
> + int fd)
> +{
> + int queue_idx = area->u64 & VHOST_USER_VRING_IDX_MASK;
> + size_t page_size = qemu_real_host_page_size;
> + struct vhost_user *u = dev->opaque;
> + VhostUserState *user = u->user;
> + VirtIODevice *vdev = dev->vdev;
> + VhostUserHostNotifier *n;
> + void *addr;
> + char *name;
> +
> + if (!virtio_has_feature(dev->protocol_features,
> + VHOST_USER_PROTOCOL_F_HOST_NOTIFIER) ||
> + vdev == NULL || queue_idx >= virtio_get_num_queues(vdev)) {
> + return -1;
> + }
> +
> + n = &user->notifier[queue_idx];
> +
> + if (n->addr) {
> + virtio_queue_set_host_notifier_mr(vdev, queue_idx, &n->mr, false);
> + object_unparent(OBJECT(&n->mr));
> + munmap(n->addr, page_size);
> + n->addr = NULL;
> + }
> +
> + if (area->u64 & VHOST_USER_VRING_NOFD_MASK) {
> + return 0;
> + }
> +
> + /* Sanity check. */
> + if (area->size != page_size) {
> + return -1;
> + }
> +
> + addr = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED,
> + fd, area->offset);
> + if (addr == MAP_FAILED) {
> + return -1;
> + }
> +
> + name = g_strdup_printf("vhost-user/host-notifier@%p mmaps[%d]",
> + user, queue_idx);
> + memory_region_init_ram_device_ptr(&n->mr, OBJECT(vdev), name,
> + page_size, addr);
> + g_free(name);
> +
> + if (virtio_queue_set_host_notifier_mr(vdev, queue_idx, &n->mr, true)) {
> + munmap(addr, page_size);
> + return -1;
> + }
> +
> + n->addr = addr;
> + n->set = true;
> +
> + return 0;
> +}
> +
> static void slave_read(void *opaque)
> {
> struct vhost_dev *dev = opaque;
> @@ -917,6 +1017,10 @@ static void slave_read(void *opaque)
> case VHOST_USER_SLAVE_CONFIG_CHANGE_MSG :
> ret = vhost_user_slave_handle_config_change(dev);
> break;
> + case VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG:
> + ret = vhost_user_slave_handle_vring_host_notifier(dev, &payload.area,
> + fd[0]);
> + break;
> default:
> error_report("Received unexpected msg type.");
> ret = -EINVAL;
> @@ -1648,6 +1752,15 @@ VhostUserState *vhost_user_init(void)
>
> void vhost_user_cleanup(VhostUserState *user)
> {
> + int i;
> +
> + for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
> + if (user->notifier[i].addr) {
> + object_unparent(OBJECT(&user->notifier[i].mr));
> + munmap(user->notifier[i].addr, qemu_real_host_page_size);
> + user->notifier[i].addr = NULL;
> + }
> + }
> }
>
> const VhostOps user_ops = {
> diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h
> index eb8bc0d90d..fd660393a0 100644
> --- a/include/hw/virtio/vhost-user.h
> +++ b/include/hw/virtio/vhost-user.h
> @@ -9,9 +9,17 @@
> #define HW_VIRTIO_VHOST_USER_H
>
> #include "chardev/char-fe.h"
> +#include "hw/virtio/virtio.h"
> +
> +typedef struct VhostUserHostNotifier {
> + MemoryRegion mr;
> + void *addr;
> + bool set;
> +} VhostUserHostNotifier;
>
> typedef struct VhostUserState {
> CharBackend *chr;
> + VhostUserHostNotifier notifier[VIRTIO_QUEUE_MAX];
> } VhostUserState;
So this notifier is per-queue. Can't we maintain it in
NetVhostUserState then?
>
> VhostUserState *vhost_user_init(void);
> --
> 2.17.0
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