vring_map causes a huge overhead by calling memory_region_find everytime.
the vring_map is executed already on vring_setup and there is also the memory
region referenced.
Signed-off-by: Peter Lieven <p...@kamp.de>
---
hw/virtio/dataplane/vring.c | 51 +++++--------------------------------------
1 file changed, 5 insertions(+), 46 deletions(-)
diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c
index 61f6d83..cfd484f 100644
--- a/hw/virtio/dataplane/vring.c
+++ b/hw/virtio/dataplane/vring.c
@@ -53,15 +53,6 @@ out:
return NULL;
}
-static void vring_unmap(void *buffer, bool is_write)
-{
- ram_addr_t addr;
- MemoryRegion *mr;
-
- mr = qemu_ram_addr_from_host(buffer, &addr);
- memory_region_unref(mr);
-}
-
/* Map the guest's vring to host memory */
bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
{
@@ -160,7 +151,6 @@ static int get_desc(Vring *vring, VirtQueueElement *elem,
unsigned *num;
struct iovec *iov;
hwaddr *addr;
- MemoryRegion *mr;
if (desc->flags & VRING_DESC_F_WRITE) {
num = &elem->in_num;
@@ -186,13 +176,10 @@ static int get_desc(Vring *vring, VirtQueueElement *elem,
}
/* TODO handle non-contiguous memory across region boundaries */
- iov->iov_base = vring_map(&mr, desc->addr, desc->len,
- desc->flags & VRING_DESC_F_WRITE);
- if (!iov->iov_base) {
- error_report("Failed to map descriptor addr %#" PRIx64 " len %u",
- (uint64_t)desc->addr, desc->len);
+ if (desc->addr + desc->len > memory_region_size(vring->mr)) {
return -EFAULT;
}
+ iov->iov_base = (void*) memory_region_get_ram_ptr(vring->mr) + desc->addr;
/* The MemoryRegion is looked up again and unref'ed later, leave the
* ref in place. */
@@ -230,22 +217,14 @@ static int get_indirect(Vring *vring, VirtQueueElement
*elem,
do {
struct vring_desc *desc_ptr;
- MemoryRegion *mr;
/* Translate indirect descriptor */
- desc_ptr = vring_map(&mr,
- indirect->addr + found * sizeof(desc),
- sizeof(desc), false);
- if (!desc_ptr) {
- error_report("Failed to map indirect descriptor "
- "addr %#" PRIx64 " len %zu",
- (uint64_t)indirect->addr + found * sizeof(desc),
- sizeof(desc));
- vring->broken = true;
+ if (indirect->addr + (found + 1) * sizeof(desc) >
memory_region_size(vring->mr)) {
return -EFAULT;
}
+ desc_ptr = (void*) memory_region_get_ram_ptr(vring->mr) +
+ indirect->addr + found * sizeof(desc);
desc = *desc_ptr;
- memory_region_unref(mr);
/* Ensure descriptor has been loaded before accessing fields */
barrier(); /* read_barrier_depends(); */
@@ -273,23 +252,6 @@ static int get_indirect(Vring *vring, VirtQueueElement
*elem,
return 0;
}
-static void vring_unmap_element(VirtQueueElement *elem)
-{
- int i;
-
- /* This assumes that the iovecs, if changed, are never moved past
- * the end of the valid area. This is true if iovec manipulations
- * are done with iov_discard_front and iov_discard_back.
- */
- for (i = 0; i < elem->out_num; i++) {
- vring_unmap(elem->out_sg[i].iov_base, false);
- }
-
- for (i = 0; i < elem->in_num; i++) {
- vring_unmap(elem->in_sg[i].iov_base, true);
- }
-}
-
/* This looks in the virtqueue and for the first available buffer, and converts
* it to an iovec for convenient access. Since descriptors consist of some
* number of output then some number of input descriptors, it's actually two
@@ -399,7 +361,6 @@ out:
if (ret == -EFAULT) {
vring->broken = true;
}
- vring_unmap_element(elem);
return ret;
}
@@ -413,8 +374,6 @@ void vring_push(Vring *vring, VirtQueueElement *elem, int
len)
unsigned int head = elem->index;
uint16_t new;
- vring_unmap_element(elem);
-
/* Don't touch vring if a fatal error occurred */
if (vring->broken) {
return;
--
1.7.9.5
