On 07.03.23 12:16, Igor Mammedov wrote:
On Tue, 7 Mar 2023 11:25:48 +0100
Igor Mammedov <imamm...@redhat.com> wrote:
On Thu, 16 Feb 2023 12:47:52 +0100
David Hildenbrand <da...@redhat.com> wrote:
Checking whether the memory regions are equal is sufficient: if they are
equal, then most certainly the contained fd is equal.
sounds reasonable to me.
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
While on janitor duty can you fixup following?
vhost_user_get_mr_data() -> memory_region_from_host ->
-> qemu_ram_block_from_host()
for qemu_ram_block_from_host doc comment seems to out of
sync (ram_addr not longer exists)
requires a bigger rework -- especially an alternative vhost_set_mem_table()
backend call that simply consumes MemoryRegionSections.
just skimming through usage of vhost_user_get_mr_data() it looks like
we are first collecting MemoryRegionSection-s into tmp_sections
then we do vhost_commit we convert then into vhost_memory_region list
and the we are trying hard to convert addresses from the later
to back to MemoryRegions we've lost during tmp_sections conversion
all over the place.
To me it looks like we should drop conversion to vhost_dev::mem
and replace its usage with vhost_dev::mem_sections directly
to get rid of data duplication and back and forth addr<->mr conversion.
For now, let's just drop vhost_backend_can_merge().
Signed-off-by: David Hildenbrand <da...@redhat.com>
Reviewed-by: Igor Mammedov <imamm...@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 e68daa35d4..4bfaf559a7 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -2195,19 +2195,6 @@ 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;
@@ -2704,7 +2691,6 @@ 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 542e003101..9ab7bc8718 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1317,7 +1317,6 @@ 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 b7fb960fa9..9d8662aa98 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -733,11 +733,7 @@ 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,
another question, can it relly happen, i.e. having 2 abut memory sections
with the same memory region, is yes then when/why?
Unfortunately yet, because vhost relies on some hacks (sorry, but
that's what it is) to make huge pages work. The following commit
contains some details:
commit 76525114736e8f669766e69b715fa59ce8648aae
Author: Dr. David Alan Gilbert <dgilb...@redhat.com>
Date: Thu Jan 16 20:24:14 2020 +0000
vhost: Only align sections for vhost-user
I added hugepage alignment code in c1ece84e7c9 to deal with
vhost-user + postcopy which needs aligned pages when using userfault.
However, on x86 the lower 2MB of address space tends to be shotgun'd
with small fragments around the 512-640k range - e.g. video RAM, and
with HyperV synic pages tend to sit around there - again splitting
it up. The alignment code complains with a 'Section rounded to ...'
error and gives up.
Otherwise it wouldn't be needed, because flatview simplification code already
merges what's reasonable.
[I'll reply to you pother mail regarding that shortly]
--
Thanks,
David / dhildenb
