Re: [PATCH] hw/acpi: some cosmetic improvements to existing code

[Igor Mammedov <imammedo@redhat.com>]

On Wed, 21 Jul 2021 19:46:10 +0530
Ani Sinha <ani@anisinha.ca> wrote:

> All existing code using acpi_get_i386_pci_host() checks for a non-null
> return from this function call. This change brings the same check to
> acpi_pcihp_disable_root_bus() function. Also adds a comment describing
> why we unconditionally pass a truth value to the last argument when calling
> acpi_pcihp_reset() from ich9 platform.
> 
> Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug")
> 
> Signed-off-by: Ani Sinha <ani@anisinha.ca>
> ---
>  hw/acpi/ich9.c  | 1 +
>  hw/acpi/pcihp.c | 5 +++++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/hw/acpi/ich9.c b/hw/acpi/ich9.c
> index 778e27b659..58d8430eb9 100644
> --- a/hw/acpi/ich9.c
> +++ b/hw/acpi/ich9.c
> @@ -281,6 +281,7 @@ static void pm_reset(void *opaque)
>      pm->smi_en_wmask = ~0;
>  
>      if (pm->use_acpi_hotplug_bridge) {
> +        /* on root PCIE bus, we always use native or SHPC based hotplug */
I had an impression that root bus doesn't support hotplug at all,
and to have hotplug there one should attach a root-port to root bus at
start up time.

>          acpi_pcihp_reset(&pm->acpi_pci_hotplug, true);
>      }
>  
> diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c
> index f4d706e47d..856c6e1b47 100644
> --- a/hw/acpi/pcihp.c
> +++ b/hw/acpi/pcihp.c
> @@ -136,6 +136,11 @@ static void acpi_pcihp_disable_root_bus(void)
>          return;
>      }
>  
> +    if (!host) {
> +        root_hp_disabled = true;
> +        return;
> +    }
It should be a separate patch,
when this could return NULL?
If it should never be null then assert here would be better.
 
> +
>      bus = PCI_HOST_BRIDGE(host)->bus;
>      if (bus) {
>          /* setting the hotplug handler to NULL makes the bus non-hotpluggable */