Re: [Qemu-devel] [PATCH 1/2] piix: Set I440FXState member pci_info.w32 in one place

[Marcel Apfelbaum <marcel@redhat.com>]

On 06/15/2016 08:56 PM, Markus Armbruster wrote:
> Range pci_info.w32 records the location of the PCI hole.
>
> It's initialized to empty when QOM zeroes I440FXState.  That's a fine
> value for a still unknown PCI hole.
>
> i440fx_init() sets pci_info.w32.begin = below_4g_mem_size.  Changes
> the PCI hole from empty to [below_4g_mem_size, UINT64_MAX].  That's a
> bogus value.
>
> i440fx_pcihost_initfn() sets pci_info.end = IO_APIC_DEFAULT_ADDRESS.
> Since i440fx_init() ran already, this changes the PCI hole to
> [below_4g_mem_size, IO_APIC_DEFAULT_ADDRESS-1].  That's the correct
> value.
>
> Setting the bounds of the PCI hole in two separate places is
> confusing, and begs the question whether the bogus intermediate value
> could be used by something, or what would happen if we somehow managed
> to realize an i440FX device without having run the board init function
> i440fx_init() first.
>
> Avoid the confusion by setting the (constant) upper bound along with
> the lower bound in i440fx_init().
>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
>   hw/pci-host/piix.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
> index df2b0e2..c63c424 100644
> --- a/hw/pci-host/piix.c
> +++ b/hw/pci-host/piix.c
> @@ -263,7 +263,6 @@ static void i440fx_pcihost_get_pci_hole64_end(Object *obj, Visitor *v,
>   static void i440fx_pcihost_initfn(Object *obj)
>   {
>       PCIHostState *s = PCI_HOST_BRIDGE(obj);
> -    I440FXState *d = I440FX_PCI_HOST_BRIDGE(obj);
>
>       memory_region_init_io(&s->conf_mem, obj, &pci_host_conf_le_ops, s,
>                             "pci-conf-idx", 4);
> @@ -285,8 +284,6 @@ static void i440fx_pcihost_initfn(Object *obj)
>       object_property_add(obj, PCI_HOST_PROP_PCI_HOLE64_END, "int",
>                           i440fx_pcihost_get_pci_hole64_end,
>                           NULL, NULL, NULL, NULL);
> -
> -    d->pci_info.w32.end = IO_APIC_DEFAULT_ADDRESS;
>   }
>
>   static void i440fx_pcihost_realize(DeviceState *dev, Error **errp)
> @@ -348,6 +345,7 @@ PCIBus *i440fx_init(const char *host_type, const char *pci_type,
>
>       i440fx = I440FX_PCI_HOST_BRIDGE(dev);
>       i440fx->pci_info.w32.begin = below_4g_mem_size;
> +    i440fx->pci_info.w32.end = IO_APIC_DEFAULT_ADDRESS;
>
>       /* setup pci memory mapping */
>       pc_pci_as_mapping_init(OBJECT(f), f->system_memory,
>

Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>

Thanks,
Marcel