bhyve vtblk: Inform guests of disk resize events.

[jhb]

Summary

Register a resize callback with the blockif interface. When the
callback fires, update the size of the disk and notify the guest via a
configuration change interrupt.

[grehan]

usr.sbin/bhyve/pci_virtio_block.c

446

Does the lock need to be taken here ?

[jhb]

usr.sbin/bhyve/pci_virtio_block.c

446

Does the lock need to be taken here ?

I only did it to protect vbc_capacity, but if the lock isn't held when reading that field then it isn't doing much good. Hmm, I guess if we cared about the race we would need to grab the lock again in pci_vtblk_cfgread()? Maybe the race is such that we don't care? Or if cfg reads are rare, maybe it doesn't hurt to be paranoid and lock in the read?

[jhb]

usr.sbin/bhyve/pci_virtio_block.c

446

I've gone ahead and removed the lock.