On 08/11/2011 06:20 PM, Paolo Bonzini wrote:
+ qemu_mutex_lock_ramlist(); QLIST_REMOVE(block, next); QLIST_INSERT_HEAD(&ram_list.blocks, block, next); + qemu_mutex_unlock_ramlist();Theoretically qemu_get_ram_ptr should be protected. The problem is not just accessing the ramlist, it is accessing the data underneath it before anyone frees it. Luckily we can set aside that problem for now, because qemu_ram_free_from_ptr is only used by device assignment and device assignment makes VMs unmigratable.
Hmm, rethinking about it, all the loops in exec.c should be protected from the mutex. That's not too good because qemu_get_ram_ptr is a hot path for TCG. Perhaps you can also avoid the mutex entirely, and just disable the above optimization for most-recently-used-block while migration is running. It's not a complete solution, but it could be good enough until we have RAM hot-plug/hot-unplug.
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