On 06/07/2017 16:52, Peter Maydell wrote: > On 5 July 2017 at 13:21, Paolo Bonzini <pbonz...@redhat.com> wrote: >> >> >> On 04/07/2017 19:02, Peter Maydell wrote: >>> Many board models and several devices need to create auxiliary >>> regions of RAM (in addition to the main lump of 'system' memory), >>> to model static RAMs, video memory, ROMs, etc. Currently they do >>> this with a sequence like: >>> memory_region_init_ram(sram, NULL, "sram", 0x10000, &error_fatal); >>> vmstate_register_ram_global(sram); >> >> Instead of vmstate_register_ram_global, you should use >> >> vmstate_register_ram(mr, owner); >> >> You should even do it for all memory regions, probably. > > This sounds like a good thing, but it's awkward for migration > compatibility, because these callers to memory_region_init_ram() > don't call vmstate_register_ram(): > > hw/arm/highbank.c (a bug) > hw/mips/mips_malta.c (region is ro) > hw/net/dp3893x.c (prom, ro, contains mac address) > hw/pci-host/xilinx-pcie.c (dummy region; migrating wouldn't hurt) > backends/hostmem-ram.c (bug, or is migration handled elsewhere?)
It's handled by memory_region_allocate_system_memory. > and if we add an implicit call then we break migration compat > for those boards/devices. Forward migration should still work. The backwards-incompatible part would be that unused memory backend objects would have to be present on the destination as well when migrating. I think it's acceptable. >> Only memory_region_init_ram_device_ptr (which sets mr->ram_device) must >> not call vmstate_register_ram. This is a bit ugly because it requires >> inlining memory_region_init_ram_ptr into it. >> >> memory_region_init_ram_from_fd probably needs to be excluded, as well, >> based on its sole user. > > Callers of memory_region_init_ram_from_file() which don't > call vmstate_register_ram(): > backends/hostmem-ram.c Same as above. > Callers of memory_region_init_ram_ptr() which don't call > vmstate_register_ram(): > hw/misc/mmio_interface.c > -- seems to be an implementation detail of the exceute-from-device > support so maybe it doesn't need migration support ?? I think so... Paolo
