Hi!
I just added this command to GRUB. I thought it could be handy sometimes, specially on coreboot:
grub> lsmmap base_addr = 0x0, length = 0x1000, type = 0x2 base_addr = 0xf0000, length = 0x1000, type = 0x2 base_addr = 0x1000, length = 0xef000, type = 0x1 base_addr = 0xf1000, length = 0x1ff0f000, type = 0x1 grub>