[PATCH v2 02/16] vhost: Remove vhost_backend_can_merge() callback

David Hildenbrand
2023-08-25T13:23:45Z

Checking whether the memory regions are equal is sufficient: if they are
equal, then most certainly the contained fd is equal.

The whole vhost-user memslot handling is suboptimal and overly
complicated. We shouldn't have to lookup a RAM memory regions we got
notified about in vhost_user_get_mr_data() using a host pointer. But that
requires a bigger rework -- especially an alternative vhost_set_mem_table()
backend call that simply consumes MemoryRegionSections.

For now, let's just drop vhost_backend_can_merge().

Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Acked-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
hw/virtio/vhost-user.c | 14 --------------
hw/virtio/vhost-vdpa.c | 1 -
hw/virtio/vhost.c | 6 +-----
include/hw/virtio/vhost-backend.h | 4 ----
4 files changed, 1 insertion(+), 24 deletions(-)

diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 1e7553352a..e6de930872 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -2205,19 +2205,6 @@ static int vhost_user_migration_done(struct vhost_dev *dev, char* mac_addr)
return -ENOTSUP;
}

-static bool vhost_user_can_merge(struct vhost_dev *dev,
- uint64_t start1, uint64_t size1,
- uint64_t start2, uint64_t size2)
-{
- ram_addr_t offset;
- int mfd, rfd;
-
- (void)vhost_user_get_mr_data(start1, &offset, &mfd);
- (void)vhost_user_get_mr_data(start2, &offset, &rfd);
-
- return mfd == rfd;
-}
-
static int vhost_user_net_set_mtu(struct vhost_dev *dev, uint16_t mtu)
{
VhostUserMsg msg;
@@ -2764,7 +2751,6 @@ const VhostOps user_ops = {
.vhost_set_vring_enable = vhost_user_set_vring_enable,
.vhost_requires_shm_log = vhost_user_requires_shm_log,
.vhost_migration_done = vhost_user_migration_done,
- .vhost_backend_can_merge = vhost_user_can_merge,
.vhost_net_set_mtu = vhost_user_net_set_mtu,
.vhost_set_iotlb_callback = vhost_user_set_iotlb_callback,
.vhost_send_device_iotlb_msg = vhost_user_send_device_iotlb_msg,
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 42f2a4bae9..8f07bee041 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1508,7 +1508,6 @@ const VhostOps vdpa_ops = {
.vhost_set_config = vhost_vdpa_set_config,
.vhost_requires_shm_log = NULL,
.vhost_migration_done = NULL,
- .vhost_backend_can_merge = NULL,
.vhost_net_set_mtu = NULL,
.vhost_set_iotlb_callback = NULL,
.vhost_send_device_iotlb_msg = NULL,
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index c1e6148833..c16ad14535 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -728,11 +728,7 @@ static void vhost_region_add_section(struct vhost_dev *dev,
size_t offset = mrs_gpa - prev_gpa_start;

if (prev_host_start + offset == mrs_host &&
- section->mr == prev_sec->mr &&
- (!dev->vhost_ops->vhost_backend_can_merge ||
- dev->vhost_ops->vhost_backend_can_merge(dev,
- mrs_host, mrs_size,
- prev_host_start, prev_size))) {
+ section->mr == prev_sec->mr) {
uint64_t max_end = MAX(prev_host_end, mrs_host + mrs_size);
need_add = false;
prev_sec->offset_within_address_space =
diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index df2821ddae..12d578824b 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -86,9 +86,6 @@ typedef int (*vhost_set_vring_enable_op)(struct vhost_dev *dev,
typedef bool (*vhost_requires_shm_log_op)(struct vhost_dev *dev);
typedef int (*vhost_migration_done_op)(struct vhost_dev *dev,
char *mac_addr);
-typedef bool (*vhost_backend_can_merge_op)(struct vhost_dev *dev,
- uint64_t start1, uint64_t size1,
- uint64_t start2, uint64_t size2);
typedef int (*vhost_vsock_set_guest_cid_op)(struct vhost_dev *dev,
uint64_t guest_cid);
typedef int (*vhost_vsock_set_running_op)(struct vhost_dev *dev, int start);
@@ -163,7 +160,6 @@ typedef struct VhostOps {
vhost_set_vring_enable_op vhost_set_vring_enable;
vhost_requires_shm_log_op vhost_requires_shm_log;
vhost_migration_done_op vhost_migration_done;
- vhost_backend_can_merge_op vhost_backend_can_merge;
vhost_vsock_set_guest_cid_op vhost_vsock_set_guest_cid;
vhost_vsock_set_running_op vhost_vsock_set_running;
vhost_set_iotlb_callback_op vhost_set_iotlb_callback;
--
2.41.0