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

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Sep 03, 2020 at 03:41:13PM +0530, Ani Sinha 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 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

OK so patch looks good, but please add all this in the commit log.

-- 
MST