Re: [PATCH] Fix a gap where acpi_pcihp_find_hotplug_bus() returns a non-hotpluggable bus

[Ani Sinha]

On Thu, Sep 3, 2020 at 3:41 PM Ani Sinha <ani@anisinha.ca> wrote:
>
> On Sep 3, 2020, 15:35 +0530, Michael S. Tsirkin <mst@redhat.com>, wrote:
>
> On Sat, Aug 29, 2020 at 01:42:33PM +0530, Ani Sinha wrote:
>
> When ACPI hotplug for the root bus is disabled, the bsel property for that
>
> bus is not set. Please see the following commit:
>
>
> 3d7e78aa7777f ("Introduce a new flag for i440fx to disable PCI hotplug on the 
> root bus").
>
>
> As a result, when acpi_pcihp_find_hotplug_bus() is called
>
> with bsel set to 0, it may return the root bus. This would be wrong since the
>
> root bus is not hotpluggable. In general, this can potentially happen to other
>
> buses as well.
>
> In this patch, we fix the issue in this function by checking if the bus 
> returned
>
> by the function is actually hotpluggable. If not, we simply return NULL. This
>
> avoids the scenario where we are actually returning a non-hotpluggable bus.
>
>
> Signed-off-by: Ani Sinha <ani@anisinha.ca>
>
>
> What exactly are the consequences though?
>
>
> The root bus

s/root bus/any device on the root bus
sorry.

might get ejected by the user when it should not if the user does the following:
>
> outl 0xae10 0
> outl 0xae08 your_slot
>
> Please see Julia’s comment:
> https://www.mail-archive.com/qemu-devel@nongnu.org/msg734548.html
>