We support coordinated discarding of RAM using the RamDiscardMgr. Let's
unlock support for coordinated discards, keeping uncoordinated discards
(e.g., via virtio-balloon) disabled.
This unlocks virtio-mem + vfio. Note that vfio used via "nvme://" by the
block layer has to be implemented/unlocked separately. For now,
virtio-mem only supports x86-64 - spapr IOMMUs are not tested/affected.
Note: The block size of a virtio-mem device has to be set to sane sizes,
depending on the maximum hotplug size - to not run out of vfio mappings.
The default virtio-mem block size is usually in the range of a couple of
MBs. The maximum number of mapping is 64k, shared with other users.
Assume you want to hotplug 256GB using virtio-mem - the block size would
have to be set to at least 8 MiB (resulting in 32768 separate mappings).
Reviewed-by: Pankaj Gupta <pankaj.gu...@cloud.ionos.com>
Cc: Paolo Bonzini <pbonz...@redhat.com>
Cc: "Michael S. Tsirkin" <m...@redhat.com>
Cc: Alex Williamson <alex.william...@redhat.com>
Cc: Dr. David Alan Gilbert <dgilb...@redhat.com>
Cc: Igor Mammedov <imamm...@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.li...@gmail.com>
Cc: Peter Xu <pet...@redhat.com>
Cc: Auger Eric <eric.au...@redhat.com>
Cc: Wei Yang <richard.weiy...@linux.alibaba.com>
Cc: teawater <teawat...@linux.alibaba.com>
Cc: Marek Kedzierski <mkedz...@redhat.com>
Signed-off-by: David Hildenbrand <da...@redhat.com>
---
hw/vfio/common.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 57c83a2f14..3ce5e26bab 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1974,8 +1974,10 @@ static int vfio_connect_container(VFIOGroup *group,
AddressSpace *as,
* new memory, it will not yet set ram_block_discard_set_required() and
* therefore, neither stops us here or deals with the sudden memory
* consumption of inflated memory.
+ *
+ * We do support discarding of memory coordinated via the RamDiscardMgr.
*/
- ret = ram_block_discard_disable(true);
+ ret = ram_block_uncoordinated_discard_disable(true);
if (ret) {
error_setg_errno(errp, -ret, "Cannot set discarding of RAM broken");
return ret;
@@ -2155,7 +2157,7 @@ close_fd_exit:
close(fd);
put_space_exit:
- ram_block_discard_disable(false);
+ ram_block_uncoordinated_discard_disable(false);
vfio_put_address_space(space);
return ret;
@@ -2277,7 +2279,7 @@ void vfio_put_group(VFIOGroup *group)
}
if (!group->ram_block_discard_allowed) {
- ram_block_discard_disable(false);
+ ram_block_uncoordinated_discard_disable(false);
}
vfio_kvm_device_del_group(group);
vfio_disconnect_container(group);
@@ -2331,7 +2333,7 @@ int vfio_get_device(VFIOGroup *group, const char *name,
if (!group->ram_block_discard_allowed) {
group->ram_block_discard_allowed = true;
- ram_block_discard_disable(false);
+ ram_block_uncoordinated_discard_disable(false);
}
}
--
2.29.2
