Patch "virtio-mem: don't read big block size in Sub Block Mode" has been added to the 5.13-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    virtio-mem: don't read big block size in Sub Block Mode

to the 5.13-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     virtio-mem-don-t-read-big-block-size-in-sub-block-mo.patch
and it can be found in the queue-5.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 58e7c9660c3a6fa414983bea16a0582301f5bad5
Author: David Hildenbrand <david@xxxxxxxxxx>
Date:   Wed Jun 2 20:57:14 2021 +0200

    virtio-mem: don't read big block size in Sub Block Mode
    
    [ Upstream commit 500817bf5e110ad9b7138bc582971bb7ee77d6f7 ]
    
    We are reading a Big Block Mode value while in Sub Block Mode
    when 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")
    Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20210602185720.31821-2-david@xxxxxxxxxx
    Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 10ec60d81e84..3bf08b5bb359 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -2420,6 +2420,10 @@ static int virtio_mem_init(struct virtio_mem *vm)
 		dev_warn(&vm->vdev->dev,
 			 "Some device memory is not addressable/pluggable. 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:
@@ -2466,14 +2470,11 @@ static int virtio_mem_init(struct virtio_mem *vm)
 		       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);