Re: [PATCH v3 2/9] hw/pci-host/q35: Inline sysbus_add_io()

[Philippe Mathieu-Daudé]

On 4/2/23 16:10, Bernhard Beschow wrote:
> sysbus_add_io() just wraps memory_region_add_subregion() while also
> obscuring where the memory is attached. So use
> memory_region_add_subregion() directly and attach it to the existing
> memory region s->mch.address_space_io which is set as an alias to
> get_system_io() by the q35 machine.
>
> Signed-off-by: Bernhard Beschow <shentey@gmail.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> ---
>   hw/pci-host/q35.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/hw/pci-host/q35.c b/hw/pci-host/q35.c
> index 26390863d6..fa05844319 100644
> --- a/hw/pci-host/q35.c
> +++ b/hw/pci-host/q35.c
> @@ -50,10 +50,12 @@ static void q35_host_realize(DeviceState *dev, Error **errp)
>       Q35PCIHost *s = Q35_HOST_DEVICE(dev);
>       SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
>   
> -    sysbus_add_io(sbd, MCH_HOST_BRIDGE_CONFIG_ADDR, &pci->conf_mem);
> +    memory_region_add_subregion(s->mch.address_space_io,
> +                                MCH_HOST_BRIDGE_CONFIG_ADDR, &pci->conf_mem);
>       sysbus_init_ioports(sbd, MCH_HOST_BRIDGE_CONFIG_ADDR, 4);

This makes me wonder why MCH_PCI_DEVICE doesn't use the bus I/O space
via pci_address_space_io(). IOW, why the MR like is in MCH_PCI_DEVICE
and not Q35_HOST_DEVICE?