Can legacy vga memory base address be defined different with architectures

[maobibo]

Hi Philippe,

    In file include/hw/pci/pci.h, the macro QEMU_PCI_VGA_MEM_BASE is defined as 
0xa0000, which represents legacy VGA memory base address. I want to know 
whether it should be the same for all architectures, or does this vga mmio 
space exist on arm64/riscv physical machines with pci host bridges?

    I ask this question because it collapses with low ddr memory space on 
Loongarch, we want to low addr memory space is continuous.

regards
bibo, mao