Revert "vhost: access vq metadata through kernel virtual address"

This reverts commit 7f466032 ("vhost: access vq metadata through
kernel virtual address").  The commit caused a bunch of issues, and
while commit 73f628ec ("vhost: disable metadata prefetch
optimization") disabled the optimization it's not nice to keep lots of
dead code around.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

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;