Re: [Qemu-devel] [PATCH 2/6] vga: increase priority of 0xa0000 memory region

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Dec 29, 2016 at 11:12:12PM +0100, Hervé Poussineau wrote:
> VGA device registers vram as BAR 0. If this BAR is activated as a very low address which
> crosses 0xa0000-0xbffff, low memory region is not accessible anymore.
> 
> This fixes display on PReP machine if we enable PCI mapping at
> address 0.

This commit message needs more information.  What exactly is the VGA
BAR colliding with?  Why does the other thing have higher priority?
Why is it safe for the VGA BAR to override the other thing?  Why is
this safe on all platforms?

> Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
> ---
>  hw/display/vga.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/display/vga.c b/hw/display/vga.c
> index 2a88b3c..c573f35 100644
> --- a/hw/display/vga.c
> +++ b/hw/display/vga.c
> @@ -2265,7 +2265,7 @@ void vga_init(VGACommonState *s, Object *obj, MemoryRegion *address_space,
>      memory_region_add_subregion_overlap(address_space,
>                                          0x000a0000,
>                                          vga_io_memory,
> -                                        1);
> +                                        2);
>      memory_region_set_coalescing(vga_io_memory);
>      if (init_vga_ports) {
>          portio_list_init(&s->vga_port_list, obj, vga_ports, s, "vga");

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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