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Subject[PATCH 1/2] Revert "vhost: access vq metadata through kernel virtual address"
Date
It was reported that metadata acceleration introduces several issues,
so this patch reverts commit ff466032dc9e5a61217f22ea34b2df932786bbfc,
73f628ec9e6bcc45b77c53fe6d0c0ec55eaf82af and
0b4a7092ffe568a55bf8f3cefdf79ff666586d91.

We will rework it on the next version.

Cc: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/vhost/vhost.c | 515 +-----------------------------------------
drivers/vhost/vhost.h | 41 ----
2 files changed, 3 insertions(+), 553 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 0536f8526359..791562e03fe0 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -298,160 +298,6 @@ static void vhost_vq_meta_reset(struct vhost_dev *d)
__vhost_vq_meta_reset(d->vqs[i]);
}

-#if VHOST_ARCH_CAN_ACCEL_UACCESS
-static void vhost_map_unprefetch(struct vhost_map *map)
-{
- kfree(map->pages);
- map->pages = NULL;
- map->npages = 0;
- map->addr = NULL;
-}
-
-static void vhost_uninit_vq_maps(struct vhost_virtqueue *vq)
-{
- struct vhost_map *map[VHOST_NUM_ADDRS];
- int i;
-
- spin_lock(&vq->mmu_lock);
- for (i = 0; i < VHOST_NUM_ADDRS; i++) {
- map[i] = rcu_dereference_protected(vq->maps[i],
- lockdep_is_held(&vq->mmu_lock));
- if (map[i])
- rcu_assign_pointer(vq->maps[i], NULL);
- }
- spin_unlock(&vq->mmu_lock);
-
- synchronize_rcu();
-
- for (i = 0; i < VHOST_NUM_ADDRS; i++)
- if (map[i])
- vhost_map_unprefetch(map[i]);
-
-}
-
-static void vhost_reset_vq_maps(struct vhost_virtqueue *vq)
-{
- int i;
-
- vhost_uninit_vq_maps(vq);
- for (i = 0; i < VHOST_NUM_ADDRS; i++)
- vq->uaddrs[i].size = 0;
-}
-
-static bool vhost_map_range_overlap(struct vhost_uaddr *uaddr,
- unsigned long start,
- unsigned long end)
-{
- if (unlikely(!uaddr->size))
- return false;
-
- return !(end < uaddr->uaddr || start > uaddr->uaddr - 1 + uaddr->size);
-}
-
-static void vhost_invalidate_vq_start(struct vhost_virtqueue *vq,
- int index,
- unsigned long start,
- unsigned long end)
-{
- struct vhost_uaddr *uaddr = &vq->uaddrs[index];
- struct vhost_map *map;
- int i;
-
- if (!vhost_map_range_overlap(uaddr, start, end))
- return;
-
- spin_lock(&vq->mmu_lock);
- ++vq->invalidate_count;
-
- map = rcu_dereference_protected(vq->maps[index],
- lockdep_is_held(&vq->mmu_lock));
- if (map) {
- if (uaddr->write) {
- for (i = 0; i < map->npages; i++)
- set_page_dirty(map->pages[i]);
- }
- rcu_assign_pointer(vq->maps[index], NULL);
- }
- spin_unlock(&vq->mmu_lock);
-
- if (map) {
- synchronize_rcu();
- vhost_map_unprefetch(map);
- }
-}
-
-static void vhost_invalidate_vq_end(struct vhost_virtqueue *vq,
- int index,
- unsigned long start,
- unsigned long end)
-{
- if (!vhost_map_range_overlap(&vq->uaddrs[index], start, end))
- return;
-
- spin_lock(&vq->mmu_lock);
- --vq->invalidate_count;
- spin_unlock(&vq->mmu_lock);
-}
-
-static int vhost_invalidate_range_start(struct mmu_notifier *mn,
- const struct mmu_notifier_range *range)
-{
- struct vhost_dev *dev = container_of(mn, struct vhost_dev,
- mmu_notifier);
- int i, j;
-
- if (!mmu_notifier_range_blockable(range))
- return -EAGAIN;
-
- for (i = 0; i < dev->nvqs; i++) {
- struct vhost_virtqueue *vq = dev->vqs[i];
-
- for (j = 0; j < VHOST_NUM_ADDRS; j++)
- vhost_invalidate_vq_start(vq, j,
- range->start,
- range->end);
- }
-
- return 0;
-}
-
-static void vhost_invalidate_range_end(struct mmu_notifier *mn,
- const struct mmu_notifier_range *range)
-{
- struct vhost_dev *dev = container_of(mn, struct vhost_dev,
- mmu_notifier);
- int i, j;
-
- for (i = 0; i < dev->nvqs; i++) {
- struct vhost_virtqueue *vq = dev->vqs[i];
-
- for (j = 0; j < VHOST_NUM_ADDRS; j++)
- vhost_invalidate_vq_end(vq, j,
- range->start,
- range->end);
- }
-}
-
-static const struct mmu_notifier_ops vhost_mmu_notifier_ops = {
- .invalidate_range_start = vhost_invalidate_range_start,
- .invalidate_range_end = vhost_invalidate_range_end,
-};
-
-static void vhost_init_maps(struct vhost_dev *dev)
-{
- struct vhost_virtqueue *vq;
- int i, j;
-
- dev->mmu_notifier.ops = &vhost_mmu_notifier_ops;
-
- for (i = 0; i < dev->nvqs; ++i) {
- vq = dev->vqs[i];
- for (j = 0; j < VHOST_NUM_ADDRS; j++)
- RCU_INIT_POINTER(vq->maps[j], NULL);
- }
-}
-#endif
-
static void vhost_vq_reset(struct vhost_dev *dev,
struct vhost_virtqueue *vq)
{
@@ -480,11 +326,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
vq->busyloop_timeout = 0;
vq->umem = NULL;
vq->iotlb = NULL;
- vq->invalidate_count = 0;
__vhost_vq_meta_reset(vq);
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- vhost_reset_vq_maps(vq);
-#endif
}

static int vhost_worker(void *data)
@@ -634,9 +476,7 @@ void vhost_dev_init(struct vhost_dev *dev,
INIT_LIST_HEAD(&dev->read_list);
INIT_LIST_HEAD(&dev->pending_list);
spin_lock_init(&dev->iotlb_lock);
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- vhost_init_maps(dev);
-#endif
+

for (i = 0; i < dev->nvqs; ++i) {
vq = dev->vqs[i];
@@ -645,7 +485,6 @@ void vhost_dev_init(struct vhost_dev *dev,
vq->heads = NULL;
vq->dev = dev;
mutex_init(&vq->mutex);
- spin_lock_init(&vq->mmu_lock);
vhost_vq_reset(dev, vq);
if (vq->handle_kick)
vhost_poll_init(&vq->poll, vq->handle_kick,
@@ -725,18 +564,7 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
if (err)
goto err_cgroup;

-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- err = mmu_notifier_register(&dev->mmu_notifier, dev->mm);
- if (err)
- goto err_mmu_notifier;
-#endif
-
return 0;
-
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
-err_mmu_notifier:
- vhost_dev_free_iovecs(dev);
-#endif
err_cgroup:
kthread_stop(worker);
dev->worker = NULL;
@@ -827,107 +655,6 @@ static void vhost_clear_msg(struct vhost_dev *dev)
spin_unlock(&dev->iotlb_lock);
}

-#if VHOST_ARCH_CAN_ACCEL_UACCESS
-static void vhost_setup_uaddr(struct vhost_virtqueue *vq,
- int index, unsigned long uaddr,
- size_t size, bool write)
-{
- struct vhost_uaddr *addr = &vq->uaddrs[index];
-
- addr->uaddr = uaddr;
- addr->size = size;
- addr->write = write;
-}
-
-static void vhost_setup_vq_uaddr(struct vhost_virtqueue *vq)
-{
- vhost_setup_uaddr(vq, VHOST_ADDR_DESC,
- (unsigned long)vq->desc,
- vhost_get_desc_size(vq, vq->num),
- false);
- vhost_setup_uaddr(vq, VHOST_ADDR_AVAIL,
- (unsigned long)vq->avail,
- vhost_get_avail_size(vq, vq->num),
- false);
- vhost_setup_uaddr(vq, VHOST_ADDR_USED,
- (unsigned long)vq->used,
- vhost_get_used_size(vq, vq->num),
- true);
-}
-
-static int vhost_map_prefetch(struct vhost_virtqueue *vq,
- int index)
-{
- struct vhost_map *map;
- struct vhost_uaddr *uaddr = &vq->uaddrs[index];
- struct page **pages;
- int npages = DIV_ROUND_UP(uaddr->size, PAGE_SIZE);
- int npinned;
- void *vaddr, *v;
- int err;
- int i;
-
- spin_lock(&vq->mmu_lock);
-
- err = -EFAULT;
- if (vq->invalidate_count)
- goto err;
-
- err = -ENOMEM;
- map = kmalloc(sizeof(*map), GFP_ATOMIC);
- if (!map)
- goto err;
-
- pages = kmalloc_array(npages, sizeof(struct page *), GFP_ATOMIC);
- if (!pages)
- goto err_pages;
-
- err = EFAULT;
- npinned = __get_user_pages_fast(uaddr->uaddr, npages,
- uaddr->write, pages);
- if (npinned > 0)
- release_pages(pages, npinned);
- if (npinned != npages)
- goto err_gup;
-
- for (i = 0; i < npinned; i++)
- if (PageHighMem(pages[i]))
- goto err_gup;
-
- vaddr = v = page_address(pages[0]);
-
- /* For simplicity, fallback to userspace address if VA is not
- * contigious.
- */
- for (i = 1; i < npinned; i++) {
- v += PAGE_SIZE;
- if (v != page_address(pages[i]))
- goto err_gup;
- }
-
- map->addr = vaddr + (uaddr->uaddr & (PAGE_SIZE - 1));
- map->npages = npages;
- map->pages = pages;
-
- rcu_assign_pointer(vq->maps[index], map);
- /* No need for a synchronize_rcu(). This function should be
- * called by dev->worker so we are serialized with all
- * readers.
- */
- spin_unlock(&vq->mmu_lock);
-
- return 0;
-
-err_gup:
- kfree(pages);
-err_pages:
- kfree(map);
-err:
- spin_unlock(&vq->mmu_lock);
- return err;
-}
-#endif
-
void vhost_dev_cleanup(struct vhost_dev *dev)
{
int i;
@@ -957,16 +684,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
kthread_stop(dev->worker);
dev->worker = NULL;
}
- if (dev->mm) {
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- mmu_notifier_unregister(&dev->mmu_notifier, dev->mm);
-#endif
+ if (dev->mm)
mmput(dev->mm);
- }
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- for (i = 0; i < dev->nvqs; i++)
- vhost_uninit_vq_maps(dev->vqs[i]);
-#endif
dev->mm = NULL;
}
EXPORT_SYMBOL_GPL(vhost_dev_cleanup);
@@ -1195,26 +914,6 @@ static inline void __user *__vhost_get_user(struct vhost_virtqueue *vq,

static inline int vhost_put_avail_event(struct vhost_virtqueue *vq)
{
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- struct vhost_map *map;
- struct vring_used *used;
-
- if (!vq->iotlb) {
- rcu_read_lock();
-
- map = rcu_dereference(vq->maps[VHOST_ADDR_USED]);
- if (likely(map)) {
- used = map->addr;
- *((__virtio16 *)&used->ring[vq->num]) =
- cpu_to_vhost16(vq, vq->avail_idx);
- rcu_read_unlock();
- return 0;
- }
-
- rcu_read_unlock();
- }
-#endif
-
return vhost_put_user(vq, cpu_to_vhost16(vq, vq->avail_idx),
vhost_avail_event(vq));
}
@@ -1223,27 +922,6 @@ static inline int vhost_put_used(struct vhost_virtqueue *vq,
struct vring_used_elem *head, int idx,
int count)
{
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- struct vhost_map *map;
- struct vring_used *used;
- size_t size;
-
- if (!vq->iotlb) {
- rcu_read_lock();
-
- map = rcu_dereference(vq->maps[VHOST_ADDR_USED]);
- if (likely(map)) {
- used = map->addr;
- size = count * sizeof(*head);
- memcpy(used->ring + idx, head, size);
- rcu_read_unlock();
- return 0;
- }
-
- rcu_read_unlock();
- }
-#endif
-
return vhost_copy_to_user(vq, vq->used->ring + idx, head,
count * sizeof(*head));
}
@@ -1251,25 +929,6 @@ static inline int vhost_put_used(struct vhost_virtqueue *vq,
static inline int vhost_put_used_flags(struct vhost_virtqueue *vq)

{
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- struct vhost_map *map;
- struct vring_used *used;
-
- if (!vq->iotlb) {
- rcu_read_lock();
-
- map = rcu_dereference(vq->maps[VHOST_ADDR_USED]);
- if (likely(map)) {
- used = map->addr;
- used->flags = cpu_to_vhost16(vq, vq->used_flags);
- rcu_read_unlock();
- return 0;
- }
-
- rcu_read_unlock();
- }
-#endif
-
return vhost_put_user(vq, cpu_to_vhost16(vq, vq->used_flags),
&vq->used->flags);
}
@@ -1277,25 +936,6 @@ static inline int vhost_put_used_flags(struct vhost_virtqueue *vq)
static inline int vhost_put_used_idx(struct vhost_virtqueue *vq)

{
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- struct vhost_map *map;
- struct vring_used *used;
-
- if (!vq->iotlb) {
- rcu_read_lock();
-
- map = rcu_dereference(vq->maps[VHOST_ADDR_USED]);
- if (likely(map)) {
- used = map->addr;
- used->idx = cpu_to_vhost16(vq, vq->last_used_idx);
- rcu_read_unlock();
- return 0;
- }
-
- rcu_read_unlock();
- }
-#endif
-
return vhost_put_user(vq, cpu_to_vhost16(vq, vq->last_used_idx),
&vq->used->idx);
}
@@ -1341,50 +981,12 @@ static void vhost_dev_unlock_vqs(struct vhost_dev *d)
static inline int vhost_get_avail_idx(struct vhost_virtqueue *vq,
__virtio16 *idx)
{
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- struct vhost_map *map;
- struct vring_avail *avail;
-
- if (!vq->iotlb) {
- rcu_read_lock();
-
- map = rcu_dereference(vq->maps[VHOST_ADDR_AVAIL]);
- if (likely(map)) {
- avail = map->addr;
- *idx = avail->idx;
- rcu_read_unlock();
- return 0;
- }
-
- rcu_read_unlock();
- }
-#endif
-
return vhost_get_avail(vq, *idx, &vq->avail->idx);
}

static inline int vhost_get_avail_head(struct vhost_virtqueue *vq,
__virtio16 *head, int idx)
{
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- struct vhost_map *map;
- struct vring_avail *avail;
-
- if (!vq->iotlb) {
- rcu_read_lock();
-
- map = rcu_dereference(vq->maps[VHOST_ADDR_AVAIL]);
- if (likely(map)) {
- avail = map->addr;
- *head = avail->ring[idx & (vq->num - 1)];
- rcu_read_unlock();
- return 0;
- }
-
- rcu_read_unlock();
- }
-#endif
-
return vhost_get_avail(vq, *head,
&vq->avail->ring[idx & (vq->num - 1)]);
}
@@ -1392,98 +994,24 @@ static inline int vhost_get_avail_head(struct vhost_virtqueue *vq,
static inline int vhost_get_avail_flags(struct vhost_virtqueue *vq,
__virtio16 *flags)
{
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- struct vhost_map *map;
- struct vring_avail *avail;
-
- if (!vq->iotlb) {
- rcu_read_lock();
-
- map = rcu_dereference(vq->maps[VHOST_ADDR_AVAIL]);
- if (likely(map)) {
- avail = map->addr;
- *flags = avail->flags;
- rcu_read_unlock();
- return 0;
- }
-
- rcu_read_unlock();
- }
-#endif
-
return vhost_get_avail(vq, *flags, &vq->avail->flags);
}

static inline int vhost_get_used_event(struct vhost_virtqueue *vq,
__virtio16 *event)
{
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- struct vhost_map *map;
- struct vring_avail *avail;
-
- if (!vq->iotlb) {
- rcu_read_lock();
- map = rcu_dereference(vq->maps[VHOST_ADDR_AVAIL]);
- if (likely(map)) {
- avail = map->addr;
- *event = (__virtio16)avail->ring[vq->num];
- rcu_read_unlock();
- return 0;
- }
- rcu_read_unlock();
- }
-#endif
-
return vhost_get_avail(vq, *event, vhost_used_event(vq));
}

static inline int vhost_get_used_idx(struct vhost_virtqueue *vq,
__virtio16 *idx)
{
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- struct vhost_map *map;
- struct vring_used *used;
-
- if (!vq->iotlb) {
- rcu_read_lock();
-
- map = rcu_dereference(vq->maps[VHOST_ADDR_USED]);
- if (likely(map)) {
- used = map->addr;
- *idx = used->idx;
- rcu_read_unlock();
- return 0;
- }
-
- rcu_read_unlock();
- }
-#endif
-
return vhost_get_used(vq, *idx, &vq->used->idx);
}

static inline int vhost_get_desc(struct vhost_virtqueue *vq,
struct vring_desc *desc, int idx)
{
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- struct vhost_map *map;
- struct vring_desc *d;
-
- if (!vq->iotlb) {
- rcu_read_lock();
-
- map = rcu_dereference(vq->maps[VHOST_ADDR_DESC]);
- if (likely(map)) {
- d = map->addr;
- *desc = *(d + idx);
- rcu_read_unlock();
- return 0;
- }
-
- rcu_read_unlock();
- }
-#endif
-
return vhost_copy_from_user(vq, desc, vq->desc + idx, sizeof(*desc));
}

@@ -1824,32 +1352,12 @@ static bool iotlb_access_ok(struct vhost_virtqueue *vq,
return true;
}

-#if VHOST_ARCH_CAN_ACCEL_UACCESS
-static void vhost_vq_map_prefetch(struct vhost_virtqueue *vq)
-{
- struct vhost_map __rcu *map;
- int i;
-
- for (i = 0; i < VHOST_NUM_ADDRS; i++) {
- rcu_read_lock();
- map = rcu_dereference(vq->maps[i]);
- rcu_read_unlock();
- if (unlikely(!map))
- vhost_map_prefetch(vq, i);
- }
-}
-#endif
-
int vq_meta_prefetch(struct vhost_virtqueue *vq)
{
unsigned int num = vq->num;

- if (!vq->iotlb) {
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- vhost_vq_map_prefetch(vq);
-#endif
+ if (!vq->iotlb)
return 1;
- }

return iotlb_access_ok(vq, VHOST_ACCESS_RO, (u64)(uintptr_t)vq->desc,
vhost_get_desc_size(vq, num), VHOST_ADDR_DESC) &&
@@ -2060,16 +1568,6 @@ static long vhost_vring_set_num_addr(struct vhost_dev *d,

mutex_lock(&vq->mutex);

-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- /* Unregister MMU notifer to allow invalidation callback
- * can access vq->uaddrs[] without holding a lock.
- */
- if (d->mm)
- mmu_notifier_unregister(&d->mmu_notifier, d->mm);
-
- vhost_uninit_vq_maps(vq);
-#endif
-
switch (ioctl) {
case VHOST_SET_VRING_NUM:
r = vhost_vring_set_num(d, vq, argp);
@@ -2081,13 +1579,6 @@ static long vhost_vring_set_num_addr(struct vhost_dev *d,
BUG();
}

-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- vhost_setup_vq_uaddr(vq);
-
- if (d->mm)
- mmu_notifier_register(&d->mmu_notifier, d->mm);
-#endif
-
mutex_unlock(&vq->mutex);

return r;
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 42a8c2a13ab1..e9ed2722b633 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -12,9 +12,6 @@
#include <linux/virtio_config.h>
#include <linux/virtio_ring.h>
#include <linux/atomic.h>
-#include <linux/pagemap.h>
-#include <linux/mmu_notifier.h>
-#include <asm/cacheflush.h>

struct vhost_work;
typedef void (*vhost_work_fn_t)(struct vhost_work *work);
@@ -83,24 +80,6 @@ enum vhost_uaddr_type {
VHOST_NUM_ADDRS = 3,
};

-struct vhost_map {
- int npages;
- void *addr;
- struct page **pages;
-};
-
-struct vhost_uaddr {
- unsigned long uaddr;
- size_t size;
- bool write;
-};
-
-#if defined(CONFIG_MMU_NOTIFIER) && ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE == 0
-#define VHOST_ARCH_CAN_ACCEL_UACCESS 0
-#else
-#define VHOST_ARCH_CAN_ACCEL_UACCESS 0
-#endif
-
/* The virtqueue structure describes a queue attached to a device. */
struct vhost_virtqueue {
struct vhost_dev *dev;
@@ -111,22 +90,7 @@ struct vhost_virtqueue {
struct vring_desc __user *desc;
struct vring_avail __user *avail;
struct vring_used __user *used;
-
-#if VHOST_ARCH_CAN_ACCEL_UACCESS
- /* Read by memory accessors, modified by meta data
- * prefetching, MMU notifier and vring ioctl().
- * Synchonrized through mmu_lock (writers) and RCU (writers
- * and readers).
- */
- struct vhost_map __rcu *maps[VHOST_NUM_ADDRS];
- /* Read by MMU notifier, modified by vring ioctl(),
- * synchronized through MMU notifier
- * registering/unregistering.
- */
- struct vhost_uaddr uaddrs[VHOST_NUM_ADDRS];
-#endif
const struct vhost_umem_node *meta_iotlb[VHOST_NUM_ADDRS];
-
struct file *kick;
struct eventfd_ctx *call_ctx;
struct eventfd_ctx *error_ctx;
@@ -181,8 +145,6 @@ struct vhost_virtqueue {
bool user_be;
#endif
u32 busyloop_timeout;
- spinlock_t mmu_lock;
- int invalidate_count;
};

struct vhost_msg_node {
@@ -196,9 +158,6 @@ struct vhost_msg_node {

struct vhost_dev {
struct mm_struct *mm;
-#ifdef CONFIG_MMU_NOTIFIER
- struct mmu_notifier mmu_notifier;
-#endif
struct mutex mutex;
struct vhost_virtqueue **vqs;
int nvqs;
--
2.19.1
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