qemu-e2k/hw/virtio/vhost-shadow-virtqueue.c

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/*
* vhost shadow virtqueue
*
* SPDX-FileCopyrightText: Red Hat, Inc. 2021
* SPDX-FileContributor: Author: Eugenio Pérez <eperezma@redhat.com>
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "qemu/osdep.h"
#include "hw/virtio/vhost-shadow-virtqueue.h"
#include "qemu/error-report.h"
#include "qapi/error.h"
#include "qemu/main-loop.h"
#include "qemu/log.h"
#include "qemu/memalign.h"
#include "linux-headers/linux/vhost.h"
/**
* Validate the transport device features that both guests can use with the SVQ
* and SVQs can use with the device.
*
* @dev_features: The features
* @errp: Error pointer
*/
bool vhost_svq_valid_features(uint64_t features, Error **errp)
{
bool ok = true;
uint64_t svq_features = features;
for (uint64_t b = VIRTIO_TRANSPORT_F_START; b <= VIRTIO_TRANSPORT_F_END;
++b) {
switch (b) {
case VIRTIO_F_ANY_LAYOUT:
continue;
case VIRTIO_F_ACCESS_PLATFORM:
/* SVQ trust in the host's IOMMU to translate addresses */
case VIRTIO_F_VERSION_1:
/* SVQ trust that the guest vring is little endian */
if (!(svq_features & BIT_ULL(b))) {
svq_features |= BIT_ULL(b);
ok = false;
}
continue;
default:
if (svq_features & BIT_ULL(b)) {
svq_features &= ~BIT_ULL(b);
ok = false;
}
}
}
if (!ok) {
error_setg(errp, "SVQ Invalid device feature flags, offer: 0x%"PRIx64
", ok: 0x%"PRIx64, features, svq_features);
}
return ok;
}
/**
* Number of descriptors that the SVQ can make available from the guest.
*
* @svq: The svq
*/
static uint16_t vhost_svq_available_slots(const VhostShadowVirtqueue *svq)
{
return svq->vring.num - (svq->shadow_avail_idx - svq->shadow_used_idx);
}
/**
* Translate addresses between the qemu's virtual address and the SVQ IOVA
*
* @svq: Shadow VirtQueue
* @vaddr: Translated IOVA addresses
* @iovec: Source qemu's VA addresses
* @num: Length of iovec and minimum length of vaddr
*/
static bool vhost_svq_translate_addr(const VhostShadowVirtqueue *svq,
hwaddr *addrs, const struct iovec *iovec,
size_t num)
{
if (num == 0) {
return true;
}
for (size_t i = 0; i < num; ++i) {
DMAMap needle = {
.translated_addr = (hwaddr)(uintptr_t)iovec[i].iov_base,
.size = iovec[i].iov_len,
};
Int128 needle_last, map_last;
size_t off;
const DMAMap *map = vhost_iova_tree_find_iova(svq->iova_tree, &needle);
/*
* Map cannot be NULL since iova map contains all guest space and
* qemu already has a physical address mapped
*/
if (unlikely(!map)) {
qemu_log_mask(LOG_GUEST_ERROR,
"Invalid address 0x%"HWADDR_PRIx" given by guest",
needle.translated_addr);
return false;
}
off = needle.translated_addr - map->translated_addr;
addrs[i] = map->iova + off;
needle_last = int128_add(int128_make64(needle.translated_addr),
int128_make64(iovec[i].iov_len));
map_last = int128_make64(map->translated_addr + map->size);
if (unlikely(int128_gt(needle_last, map_last))) {
qemu_log_mask(LOG_GUEST_ERROR,
"Guest buffer expands over iova range");
return false;
}
}
return true;
}
static void vhost_vring_write_descs(VhostShadowVirtqueue *svq, hwaddr *sg,
const struct iovec *iovec, size_t num,
bool more_descs, bool write)
{
uint16_t i = svq->free_head, last = svq->free_head;
unsigned n;
uint16_t flags = write ? cpu_to_le16(VRING_DESC_F_WRITE) : 0;
vring_desc_t *descs = svq->vring.desc;
if (num == 0) {
return;
}
for (n = 0; n < num; n++) {
if (more_descs || (n + 1 < num)) {
descs[i].flags = flags | cpu_to_le16(VRING_DESC_F_NEXT);
descs[i].next = cpu_to_le16(svq->desc_next[i]);
} else {
descs[i].flags = flags;
}
descs[i].addr = cpu_to_le64(sg[n]);
descs[i].len = cpu_to_le32(iovec[n].iov_len);
last = i;
i = cpu_to_le16(svq->desc_next[i]);
}
svq->free_head = le16_to_cpu(svq->desc_next[last]);
}
static bool vhost_svq_add_split(VhostShadowVirtqueue *svq,
VirtQueueElement *elem, unsigned *head)
{
unsigned avail_idx;
vring_avail_t *avail = svq->vring.avail;
bool ok;
g_autofree hwaddr *sgs = g_new(hwaddr, MAX(elem->out_num, elem->in_num));
*head = svq->free_head;
/* We need some descriptors here */
if (unlikely(!elem->out_num && !elem->in_num)) {
qemu_log_mask(LOG_GUEST_ERROR,
"Guest provided element with no descriptors");
return false;
}
ok = vhost_svq_translate_addr(svq, sgs, elem->out_sg, elem->out_num);
if (unlikely(!ok)) {
return false;
}
vhost_vring_write_descs(svq, sgs, elem->out_sg, elem->out_num,
elem->in_num > 0, false);
ok = vhost_svq_translate_addr(svq, sgs, elem->in_sg, elem->in_num);
if (unlikely(!ok)) {
return false;
}
vhost_vring_write_descs(svq, sgs, elem->in_sg, elem->in_num, false, true);
/*
* Put the entry in the available array (but don't update avail->idx until
* they do sync).
*/
avail_idx = svq->shadow_avail_idx & (svq->vring.num - 1);
avail->ring[avail_idx] = cpu_to_le16(*head);
svq->shadow_avail_idx++;
/* Update the avail index after write the descriptor */
smp_wmb();
avail->idx = cpu_to_le16(svq->shadow_avail_idx);
return true;
}
/**
* Add an element to a SVQ.
*
* The caller must check that there is enough slots for the new element. It
* takes ownership of the element: In case of failure, it is free and the SVQ
* is considered broken.
*/
static bool vhost_svq_add(VhostShadowVirtqueue *svq, VirtQueueElement *elem)
{
unsigned qemu_head;
bool ok = vhost_svq_add_split(svq, elem, &qemu_head);
if (unlikely(!ok)) {
g_free(elem);
return false;
}
svq->ring_id_maps[qemu_head] = elem;
return true;
}
static void vhost_svq_kick(VhostShadowVirtqueue *svq)
{
/*
* We need to expose the available array entries before checking the used
* flags
*/
smp_mb();
if (svq->vring.used->flags & VRING_USED_F_NO_NOTIFY) {
return;
}
event_notifier_set(&svq->hdev_kick);
}
/**
* Forward available buffers.
*
* @svq: Shadow VirtQueue
*
* Note that this function does not guarantee that all guest's available
* buffers are available to the device in SVQ avail ring. The guest may have
* exposed a GPA / GIOVA contiguous buffer, but it may not be contiguous in
* qemu vaddr.
*
* If that happens, guest's kick notifications will be disabled until the
* device uses some buffers.
*/
static void vhost_handle_guest_kick(VhostShadowVirtqueue *svq)
{
/* Clear event notifier */
event_notifier_test_and_clear(&svq->svq_kick);
/* Forward to the device as many available buffers as possible */
do {
virtio_queue_set_notification(svq->vq, false);
while (true) {
VirtQueueElement *elem;
bool ok;
if (svq->next_guest_avail_elem) {
elem = g_steal_pointer(&svq->next_guest_avail_elem);
} else {
elem = virtqueue_pop(svq->vq, sizeof(*elem));
}
if (!elem) {
break;
}
if (elem->out_num + elem->in_num > vhost_svq_available_slots(svq)) {
/*
* This condition is possible since a contiguous buffer in GPA
* does not imply a contiguous buffer in qemu's VA
* scatter-gather segments. If that happens, the buffer exposed
* to the device needs to be a chain of descriptors at this
* moment.
*
* SVQ cannot hold more available buffers if we are here:
* queue the current guest descriptor and ignore further kicks
* until some elements are used.
*/
svq->next_guest_avail_elem = elem;
return;
}
ok = vhost_svq_add(svq, elem);
if (unlikely(!ok)) {
/* VQ is broken, just return and ignore any other kicks */
return;
}
vhost_svq_kick(svq);
}
virtio_queue_set_notification(svq->vq, true);
} while (!virtio_queue_empty(svq->vq));
}
/**
* Handle guest's kick.
*
* @n: guest kick event notifier, the one that guest set to notify svq.
*/
static void vhost_handle_guest_kick_notifier(EventNotifier *n)
{
VhostShadowVirtqueue *svq = container_of(n, VhostShadowVirtqueue, svq_kick);
event_notifier_test_and_clear(n);
vhost_handle_guest_kick(svq);
}
static bool vhost_svq_more_used(VhostShadowVirtqueue *svq)
{
if (svq->last_used_idx != svq->shadow_used_idx) {
return true;
}
svq->shadow_used_idx = cpu_to_le16(svq->vring.used->idx);
return svq->last_used_idx != svq->shadow_used_idx;
}
/**
* Enable vhost device calls after disable them.
*
* @svq: The svq
*
* It returns false if there are pending used buffers from the vhost device,
* avoiding the possible races between SVQ checking for more work and enabling
* callbacks. True if SVQ used vring has no more pending buffers.
*/
static bool vhost_svq_enable_notification(VhostShadowVirtqueue *svq)
{
svq->vring.avail->flags &= ~cpu_to_le16(VRING_AVAIL_F_NO_INTERRUPT);
/* Make sure the flag is written before the read of used_idx */
smp_mb();
return !vhost_svq_more_used(svq);
}
static void vhost_svq_disable_notification(VhostShadowVirtqueue *svq)
{
svq->vring.avail->flags |= cpu_to_le16(VRING_AVAIL_F_NO_INTERRUPT);
}
static uint16_t vhost_svq_last_desc_of_chain(const VhostShadowVirtqueue *svq,
uint16_t num, uint16_t i)
{
for (uint16_t j = 0; j < (num - 1); ++j) {
i = le16_to_cpu(svq->desc_next[i]);
}
return i;
}
static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq,
uint32_t *len)
{
const vring_used_t *used = svq->vring.used;
vring_used_elem_t used_elem;
uint16_t last_used, last_used_chain, num;
if (!vhost_svq_more_used(svq)) {
return NULL;
}
/* Only get used array entries after they have been exposed by dev */
smp_rmb();
last_used = svq->last_used_idx & (svq->vring.num - 1);
used_elem.id = le32_to_cpu(used->ring[last_used].id);
used_elem.len = le32_to_cpu(used->ring[last_used].len);
svq->last_used_idx++;
if (unlikely(used_elem.id >= svq->vring.num)) {
qemu_log_mask(LOG_GUEST_ERROR, "Device %s says index %u is used",
svq->vdev->name, used_elem.id);
return NULL;
}
if (unlikely(!svq->ring_id_maps[used_elem.id])) {
qemu_log_mask(LOG_GUEST_ERROR,
"Device %s says index %u is used, but it was not available",
svq->vdev->name, used_elem.id);
return NULL;
}
num = svq->ring_id_maps[used_elem.id]->in_num +
svq->ring_id_maps[used_elem.id]->out_num;
last_used_chain = vhost_svq_last_desc_of_chain(svq, num, used_elem.id);
svq->desc_next[last_used_chain] = svq->free_head;
svq->free_head = used_elem.id;
*len = used_elem.len;
return g_steal_pointer(&svq->ring_id_maps[used_elem.id]);
}
static void vhost_svq_flush(VhostShadowVirtqueue *svq,
bool check_for_avail_queue)
{
VirtQueue *vq = svq->vq;
/* Forward as many used buffers as possible. */
do {
unsigned i = 0;
vhost_svq_disable_notification(svq);
while (true) {
uint32_t len;
g_autofree VirtQueueElement *elem = vhost_svq_get_buf(svq, &len);
if (!elem) {
break;
}
if (unlikely(i >= svq->vring.num)) {
qemu_log_mask(LOG_GUEST_ERROR,
"More than %u used buffers obtained in a %u size SVQ",
i, svq->vring.num);
virtqueue_fill(vq, elem, len, i);
virtqueue_flush(vq, i);
return;
}
virtqueue_fill(vq, elem, len, i++);
}
virtqueue_flush(vq, i);
event_notifier_set(&svq->svq_call);
if (check_for_avail_queue && svq->next_guest_avail_elem) {
/*
* Avail ring was full when vhost_svq_flush was called, so it's a
* good moment to make more descriptors available if possible.
*/
vhost_handle_guest_kick(svq);
}
} while (!vhost_svq_enable_notification(svq));
}
/**
* Forward used buffers.
*
* @n: hdev call event notifier, the one that device set to notify svq.
*
* Note that we are not making any buffers available in the loop, there is no
* way that it runs more than virtqueue size times.
*/
static void vhost_svq_handle_call(EventNotifier *n)
{
VhostShadowVirtqueue *svq = container_of(n, VhostShadowVirtqueue,
hdev_call);
event_notifier_test_and_clear(n);
vhost_svq_flush(svq, true);
}
/**
* Set the call notifier for the SVQ to call the guest
*
* @svq: Shadow virtqueue
* @call_fd: call notifier
*
* Called on BQL context.
*/
void vhost_svq_set_svq_call_fd(VhostShadowVirtqueue *svq, int call_fd)
{
if (call_fd == VHOST_FILE_UNBIND) {
/*
* Fail event_notifier_set if called handling device call.
*
* SVQ still needs device notifications, since it needs to keep
* forwarding used buffers even with the unbind.
*/
memset(&svq->svq_call, 0, sizeof(svq->svq_call));
} else {
event_notifier_init_fd(&svq->svq_call, call_fd);
}
}
/**
* Get the shadow vq vring address.
* @svq: Shadow virtqueue
* @addr: Destination to store address
*/
void vhost_svq_get_vring_addr(const VhostShadowVirtqueue *svq,
struct vhost_vring_addr *addr)
{
addr->desc_user_addr = (uint64_t)(uintptr_t)svq->vring.desc;
addr->avail_user_addr = (uint64_t)(uintptr_t)svq->vring.avail;
addr->used_user_addr = (uint64_t)(uintptr_t)svq->vring.used;
}
size_t vhost_svq_driver_area_size(const VhostShadowVirtqueue *svq)
{
size_t desc_size = sizeof(vring_desc_t) * svq->vring.num;
size_t avail_size = offsetof(vring_avail_t, ring) +
sizeof(uint16_t) * svq->vring.num;
return ROUND_UP(desc_size + avail_size, qemu_real_host_page_size());
}
size_t vhost_svq_device_area_size(const VhostShadowVirtqueue *svq)
{
size_t used_size = offsetof(vring_used_t, ring) +
sizeof(vring_used_elem_t) * svq->vring.num;
return ROUND_UP(used_size, qemu_real_host_page_size());
}
/**
* Set a new file descriptor for the guest to kick the SVQ and notify for avail
*
* @svq: The svq
* @svq_kick_fd: The svq kick fd
*
* Note that the SVQ will never close the old file descriptor.
*/
void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue *svq, int svq_kick_fd)
{
EventNotifier *svq_kick = &svq->svq_kick;
bool poll_stop = VHOST_FILE_UNBIND != event_notifier_get_fd(svq_kick);
bool poll_start = svq_kick_fd != VHOST_FILE_UNBIND;
if (poll_stop) {
event_notifier_set_handler(svq_kick, NULL);
}
/*
* event_notifier_set_handler already checks for guest's notifications if
* they arrive at the new file descriptor in the switch, so there is no
* need to explicitly check for them.
*/
if (poll_start) {
event_notifier_init_fd(svq_kick, svq_kick_fd);
event_notifier_set(svq_kick);
event_notifier_set_handler(svq_kick, vhost_handle_guest_kick_notifier);
}
}
/**
* Start the shadow virtqueue operation.
*
* @svq: Shadow Virtqueue
* @vdev: VirtIO device
* @vq: Virtqueue to shadow
*/
void vhost_svq_start(VhostShadowVirtqueue *svq, VirtIODevice *vdev,
VirtQueue *vq)
{
size_t desc_size, driver_size, device_size;
svq->next_guest_avail_elem = NULL;
svq->shadow_avail_idx = 0;
svq->shadow_used_idx = 0;
svq->last_used_idx = 0;
svq->vdev = vdev;
svq->vq = vq;
svq->vring.num = virtio_queue_get_num(vdev, virtio_get_queue_index(vq));
driver_size = vhost_svq_driver_area_size(svq);
device_size = vhost_svq_device_area_size(svq);
svq->vring.desc = qemu_memalign(qemu_real_host_page_size(), driver_size);
desc_size = sizeof(vring_desc_t) * svq->vring.num;
svq->vring.avail = (void *)((char *)svq->vring.desc + desc_size);
memset(svq->vring.desc, 0, driver_size);
svq->vring.used = qemu_memalign(qemu_real_host_page_size(), device_size);
memset(svq->vring.used, 0, device_size);
svq->ring_id_maps = g_new0(VirtQueueElement *, svq->vring.num);
svq->desc_next = g_new0(uint16_t, svq->vring.num);
for (unsigned i = 0; i < svq->vring.num - 1; i++) {
svq->desc_next[i] = cpu_to_le16(i + 1);
}
}
/**
* Stop the shadow virtqueue operation.
* @svq: Shadow Virtqueue
*/
void vhost_svq_stop(VhostShadowVirtqueue *svq)
{
event_notifier_set_handler(&svq->svq_kick, NULL);
g_autofree VirtQueueElement *next_avail_elem = NULL;
if (!svq->vq) {
return;
}
/* Send all pending used descriptors to guest */
vhost_svq_flush(svq, false);
for (unsigned i = 0; i < svq->vring.num; ++i) {
g_autofree VirtQueueElement *elem = NULL;
elem = g_steal_pointer(&svq->ring_id_maps[i]);
if (elem) {
virtqueue_detach_element(svq->vq, elem, 0);
}
}
next_avail_elem = g_steal_pointer(&svq->next_guest_avail_elem);
if (next_avail_elem) {
virtqueue_detach_element(svq->vq, next_avail_elem, 0);
}
svq->vq = NULL;
g_free(svq->desc_next);
g_free(svq->ring_id_maps);
qemu_vfree(svq->vring.desc);
qemu_vfree(svq->vring.used);
}
/**
* Creates vhost shadow virtqueue, and instructs the vhost device to use the
* shadow methods and file descriptors.
*
* @iova_tree: Tree to perform descriptors translations
*
* Returns the new virtqueue or NULL.
*
* In case of error, reason is reported through error_report.
*/
VhostShadowVirtqueue *vhost_svq_new(VhostIOVATree *iova_tree)
{
g_autofree VhostShadowVirtqueue *svq = g_new0(VhostShadowVirtqueue, 1);
int r;
r = event_notifier_init(&svq->hdev_kick, 0);
if (r != 0) {
error_report("Couldn't create kick event notifier: %s (%d)",
g_strerror(errno), errno);
goto err_init_hdev_kick;
}
r = event_notifier_init(&svq->hdev_call, 0);
if (r != 0) {
error_report("Couldn't create call event notifier: %s (%d)",
g_strerror(errno), errno);
goto err_init_hdev_call;
}
event_notifier_init_fd(&svq->svq_kick, VHOST_FILE_UNBIND);
event_notifier_set_handler(&svq->hdev_call, vhost_svq_handle_call);
svq->iova_tree = iova_tree;
return g_steal_pointer(&svq);
err_init_hdev_call:
event_notifier_cleanup(&svq->hdev_kick);
err_init_hdev_kick:
return NULL;
}
/**
* Free the resources of the shadow virtqueue.
*
* @pvq: gpointer to SVQ so it can be used by autofree functions.
*/
void vhost_svq_free(gpointer pvq)
{
VhostShadowVirtqueue *vq = pvq;
vhost_svq_stop(vq);
event_notifier_cleanup(&vq->hdev_kick);
event_notifier_set_handler(&vq->hdev_call, NULL);
event_notifier_cleanup(&vq->hdev_call);
g_free(vq);
}