We are reading the a BBM (Big Block Mode) value while in SBM (Sub Block
Mode) while initializing. Fortunately, vm->bbm.bb_size maps to some counter
in the vm->sbm.mb_count array, which is 0 at that point in time.
No harm done; still, this was unintended and is not future-proof.
Fixes: 4ba50cd3355d ("virtio-mem: Big Block Mode (BBM) memory hotplug")
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Marek Kedzierski <mkedzier@xxxxxxxxxx>
Cc: Hui Zhu <teawater@xxxxxxxxx>
Cc: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx>
Cc: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
drivers/virtio/virtio_mem.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 9fc9ec4a25f5..6d4e01c4e2fa 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -2409,6 +2409,10 @@ static int virtio_mem_init(struct virtio_mem *vm)
dev_warn(&vm->vdev->dev,
"Some memory is not addressable. This can make some memory unusable.\n");
+ /* Prepare the offline threshold - make sure we can add two blocks. */
+ vm->offline_threshold = max_t(uint64_t, 2 * memory_block_size_bytes(),
+ VIRTIO_MEM_DEFAULT_OFFLINE_THRESHOLD);
+
/*
* We want subblocks to span at least MAX_ORDER_NR_PAGES and
* pageblock_nr_pages pages. This:
@@ -2453,14 +2457,11 @@ static int virtio_mem_init(struct virtio_mem *vm)
addr = vm->addr + vm->bbm.bb_size - 1;
vm->bbm.first_bb_id = virtio_mem_phys_to_bb_id(vm, addr);
vm->bbm.next_bb_id = vm->bbm.first_bb_id;
- }
- /* Prepare the offline threshold - make sure we can add two blocks. */
- vm->offline_threshold = max_t(uint64_t, 2 * memory_block_size_bytes(),
- VIRTIO_MEM_DEFAULT_OFFLINE_THRESHOLD);
- /* In BBM, we also want at least two big blocks. */
- vm->offline_threshold = max_t(uint64_t, 2 * vm->bbm.bb_size,
- vm->offline_threshold);
+ /* Make sure we can add two big blocks. */
+ vm->offline_threshold = max_t(uint64_t, 2 * vm->bbm.bb_size,
+ vm->offline_threshold);
+ }
dev_info(&vm->vdev->dev, "start address: 0x%llx", vm->addr);
dev_info(&vm->vdev->dev, "region size: 0x%llx", vm->region_size);
--
2.29.2
