Re: [edk2-devel] [PATCH] MdeModulePkg/PciBusDxe: plug device hierarchy leak upon bridge hot-unplug

["Laszlo Ersek" <lersek@redhat.com>]

On 2/20/24 20:48, Hsueh, Hong-Chih (Neo) wrote:
> [AMD Official Use Only - General]
> 
> 
> Hi Feng & Laszlo,
> 
> Thank you for the feedback, I have changed the title of this email and
> the title of the commit message of this patch.
> The new patch as attached. If this patch looks good to you, could you
> please help to add reviewed-by?

Please post the patch (with "v2" in the subject prefix) to the mailing
list, as a standalone thread-starter.

Thanks,
Laszlo


> 
> Thanks!
> 
> Regards,
> Neo
> 
> ------------------------------------------------------------------------
> *From:* Ding, Feng (Sunnyvale) <feng1.ding@amd.com>
> *Sent:* Thursday, February 8, 2024 5:09 PM
> *To:* Laszlo Ersek <lersek@redhat.com>; devel@edk2.groups.io
> <devel@edk2.groups.io>; Hsueh, Hong-Chih (Neo) <Hong-Chih.Hsueh@amd.com>
> *Cc:* He, Jiangang <Jiangang.He@amd.com>; Chang, Abner
> <Abner.Chang@amd.com>; ray.ni@intel.com <ray.ni@intel.com>;
> gaoliming@byosoft.com.cn <gaoliming@byosoft.com.cn>; Gopal, Pradeep
> <Pradeep.Gopal@amd.com>
> *Subject:* RE: [edk2-devel] [PATCH] MdeModulePkg/PciBusDxe: Fix hotplug
> functionality for USB4 bridge
>  
> [AMD Official Use Only - General]
> 
> Hi Laszlo,
> 
> " MdeModulePkg/PciBusDxe: plug device hierarchy leak upon bridge
> hot-unplug " is perfect description for the issue.
> "a root bridge" is "a (PCIe Hotplug) bridge", locating anywhere.
> 
> Thanks
> feng
> 
> -----Original Message-----
> From: Laszlo Ersek <lersek@redhat.com>
> Sent: Wednesday, February 7, 2024 12:51 PM
> To: devel@edk2.groups.io; Hsueh, Hong-Chih (Neo) <Hong-Chih.Hsueh@amd.com>
> Cc: Ding, Feng (Sunnyvale) <feng1.ding@amd.com>; He, Jiangang
> <Jiangang.He@amd.com>; Chang, Abner <Abner.Chang@amd.com>;
> ray.ni@intel.com; gaoliming@byosoft.com.cn
> Subject: Re: [edk2-devel] [PATCH] MdeModulePkg/PciBusDxe: Fix hotplug
> functionality for USB4 bridge
> 
> Caution: This message originated from an External Source. Use proper
> caution when opening attachments, clicking links, or responding.
> 
> 
> On 2/6/24 23:34, Hsueh, Hong-Chih (Neo) via groups.io wrote:
>> A USB4 or TBT bridge can be plugged or unplugged on USB4 port. The actions require PciHotPlugRequestNotify to add a root bridge or remove a root bridge completely.
>> In the plug-unplug-plug scenerio, PciHotPlugRequestNotify will return with no-action on second plug because bridge tree shows configured.
>> Destroy Pci Device Tree in function PciHotPlugRequestNotify for unplug event to fix this issue.
>>
>> Cc: Feng Ding <feng1.ding@amd.com>
>> Cc: Jiangang He <jiangang.he@amd.com>
>> Signed-off-by: Neo Hsueh <Hong-Chih.Hsueh@amd.com>
>> ---
>>  MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumerator.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumerator.c b/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumerator.c
>> index 3f8c6e6da7..2b7af60e0a 100644
>> --- a/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumerator.c
>> +++ b/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumerator.c
>> @@ -2103,6 +2103,8 @@ PciHotPlugRequestNotify (
>>        }
>>      }
>>
>> +    DestroyPciDeviceTree (Bridge);
>> +
>>      //
>>      // End for
>>      //
> 
> I think the subject line is too specific. This patch appears to fix a
> general resource leak in the PCI hot-unplug functionality. Writing up
> the USB4 angle in the commit message is welcome in my opinion, but the
> subject should state something like:
> 
> MdeModulePkg/PciBusDxe: plug device hierarchy leak upon bridge hot-unplug
> 
> (And I think the bridge doesn't even have to be a *root* bridge for the
> leak to occur; is that right?)
> 
> Laszlo
> 



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