Re: [PATCH-for-5.2 v2] hw/i386/acpi-build: Fix maybe-uninitialized error when ACPI hotplug off

[Ani Sinha]

On Sun, Nov 8, 2020 at 1:10 AM Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
>
> GCC 9.3.0 thinks that 'method' can be left uninitialized. This code
> is already in the "if (bsel || pcihp_bridge_en)" block statement,
> but it isn't smart enough to figure it out.
>
> Restrict the code to be used only in the "if (bsel || pcihp_bridge_en)"
> block statement to fix (on Ubuntu):
>
>   ../hw/i386/acpi-build.c: In function 'build_append_pci_bus_devices':
>   ../hw/i386/acpi-build.c:496:9: error: 'method' may be used uninitialized
>   in this function [-Werror=maybe-uninitialized]
>     496 |         aml_append(parent_scope, method);
>         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   cc1: all warnings being treated as errors

OK I looked at the patch closely and it makes sense. Can you please
run a "make check" to make sure we have not broken anything?

>
> Fixes: df4008c9c59 ("piix4: don't reserve hw resources when hotplug is off 
> globally")
Acked-by: Ani Sinha <ani@anisinha.ca>

> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  hw/i386/acpi-build.c | 45 +++++++++++++++++++++-----------------------
>  1 file changed, 21 insertions(+), 24 deletions(-)
>
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 4f66642d887..1f5c2112452 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -465,34 +465,31 @@ static void build_append_pci_bus_devices(Aml 
> *parent_scope, PCIBus *bus,
>       */
>      if (bsel || pcihp_bridge_en) {
>          method = aml_method("PCNT", 0, AML_NOTSERIALIZED);
> -    }
> -    /* If bus supports hotplug select it and notify about local events */
> -    if (bsel) {
> -        uint64_t bsel_val = qnum_get_uint(qobject_to(QNum, bsel));
>
> -        aml_append(method, aml_store(aml_int(bsel_val), aml_name("BNUM")));
> -        aml_append(method,
> -            aml_call2("DVNT", aml_name("PCIU"), aml_int(1) /* Device Check 
> */)
> -        );
> -        aml_append(method,
> -            aml_call2("DVNT", aml_name("PCID"), aml_int(3)/* Eject Request 
> */)
> -        );
> -    }
> +        /* If bus supports hotplug select it and notify about local events */
> +        if (bsel) {
> +            uint64_t bsel_val = qnum_get_uint(qobject_to(QNum, bsel));
>
> -    /* Notify about child bus events in any case */
> -    if (pcihp_bridge_en) {
> -        QLIST_FOREACH(sec, &bus->child, sibling) {
> -            int32_t devfn = sec->parent_dev->devfn;
> -
> -            if (pci_bus_is_root(sec) || pci_bus_is_express(sec)) {
> -                continue;
> -            }
> -
> -            aml_append(method, aml_name("^S%.02X.PCNT", devfn));
> +            aml_append(method, aml_store(aml_int(bsel_val), 
> aml_name("BNUM")));
> +            aml_append(method, aml_call2("DVNT", aml_name("PCIU"),
> +                                         aml_int(1))); /* Device Check */
> +            aml_append(method, aml_call2("DVNT", aml_name("PCID"),
> +                                         aml_int(3))); /* Eject Request */
> +        }
> +
> +        /* Notify about child bus events in any case */
> +        if (pcihp_bridge_en) {
> +            QLIST_FOREACH(sec, &bus->child, sibling) {
> +                int32_t devfn = sec->parent_dev->devfn;
> +
> +                if (pci_bus_is_root(sec) || pci_bus_is_express(sec)) {
> +                    continue;
> +                }
> +
> +                aml_append(method, aml_name("^S%.02X.PCNT", devfn));
> +            }
>          }
> -    }
>
> -    if (bsel || pcihp_bridge_en) {
>          aml_append(parent_scope, method);
>      }
>      qobject_unref(bsel);
> --
> 2.26.2
>