On 11/24/2015 08:05 PM, Paolo Bonzini wrote: > > > On 24/11/2015 04:10, Fam Zheng wrote: >> What about all the hot-plug commands that changes the memory layout? > > If the guest is stopped, they shouldn't. device_add does not enable new > BARs for example, the guest does that after it receives the ACPI event > for PCI hotplug (or similarly an interrupt for SHPC or PCIe hotplug). > > Actually I like the idea of background dump, and a separate thread is an > obvious way to do it since QEMU's memory API is mostly thread safe. > > However, qmp_dump_guest_memory should only proceed if the VM is stopped > and is not in incoming migration (RUN_STATE_INMIGRATE); as you prefer. > If the VM is stopped, there is no whack-a-mole; the memory should not be > touched after vm_stop returns. The only special case is incoming migration. > > Regarding thread-safety, the thread needs to take > qemu_mutex_ram_list_lock or rcu_read_lock in order to get the list of > RAM regions. Even better, build a list of MemoryRegions in advance > (protecting them with memory_region_ref) in the iothread, and consult it > during the dump. At the end you can use memory_region_unref to release > them.
Hi, Paolo, Thanks for the comments. If any of you are interested in this function, I would like to make bold to take the ownership to move on to v2, with all the review comments adopted (it might be necessary to contain a basic query mechanism if there is a v2 patch, since I see that it's the one that most to be complaint about besides the risk that it might bring). Thanks. Peter > > Paolo >
