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what is the purpose of vgt-isa device? #3

Open mountainlion0523 opened 9 years ago

mountainlion0523 commented 9 years ago

It seems during pc_init, QEMU creates 2 pci devices : vgt-isa, vgt-vga

but it seems there isn't any read or write functions on vgt-isa is it necessary device?

l1viathan commented 9 years ago

The ISA bridge will be used by guest GPU driver, to determine offsets of some MMIO registers. So it's necessary for now.

We shares the same logic as IGD passthrough here. Once the passthrough case works without this ISA bridge, we'll leverage that effort :)