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Re: [PATCH] Fix a gap where acpi_pcihp_find_hotplug_bus() returns a non-
From: |
Michael S. Tsirkin |
Subject: |
Re: [PATCH] Fix a gap where acpi_pcihp_find_hotplug_bus() returns a non-hotpluggable bus |
Date: |
Thu, 3 Sep 2020 06:16:08 -0400 |
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