Re: [PATCH] powerpc/rtas_pci: No hotplug on permanently removed device on pSeries

[Harsh Prateek Bora <harshpb@linux.ibm.com>]

Hi Tasmiya,

There was a v2 posted here:
https://lore.kernel.org/linuxppc-dev/178246517230.1267.12206176311111155505.stgit@linux.ibm.com/

Although a minor change in return value and re-ordering before 
CONFIG_BLOCKED incorporated in v2, it's better to test v2 and provide 
test feedback on the same.

Thanks
Harsh

On 25/08/26 3:52 pm, tasmiya wrote:
> Greetings,
> 
> Tested-by: Tasmiya Nalatwad <tasmiya@linux.ibm.com>
> Reported-by: Tasmiya Nalatwad <tasmiya@linux.ibm.com>
> 
> 
> I have Tested the patch in my KVM guest environment with device 
> passthrough via vfio, It works fine and fixes the issue.
> Triggered EEH freeze beyond eeh_max_freezes to permanently remove the 
> device, then hotplugged a new PCI device. Without the patch, the rescan 
> attempted to bring back the permanently removed device. With the patch 
> applied, the removed device is correctly skipped during rescan and only 
> newly hotplugged device is seen in the guest.
> 
> 
> Thank you,
> 
> Tasmiya
> 
> 
> On 27/04/26 8:25 am, Shivaprasad G Bhat wrote:
>> The eeh_driver disables and offlines the PE permanently when it
>> exceeds the freeze count beyond eeh_max_freeze within the last hour.
>> The PE is only offline, so the device tree entries, eeh device
>> references are all intact till the real unplug of the device from
>> the guest/host takes place.
>>
>> On pSeries, with a new hotplug of any PCI device, the drmgr initiates
>> a system-wide PCI rescan, which finds devices offlined by the eeh_driver
>> and there will be attempts to bring them online. This leads to
>> recurring EEHs either at the config read time itself or a bit
>> later depending on the type of the problem.
>>
>> For PowerNV, the commit d2b0f6f77ee5 ("powerpc/eeh: No hotplug on
>> permanently removed dev") introduced the EEH_DEV_REMOVED flag to
>> prevent such inadvertent rescans on hierarchical toplogies relavent in
>> Baremetal setups. For pSeries, such topologies don't really make sense
>> as the devices are either part of the same PE OR exposed as independent
>> devices on multiple virtual PHBs. However, the inadvertent rescans are
>> still a possibility with either hotplug of a new device or otherwise
>> with manual system-wide pci bus rescan attempts.
>>
>> So the patch checks for EEH_DEV_REMOVED before allowing config space
>> access just like PowerNV, making the PCI core omit the PE, and thus
>> preventing subsequent EEH recurances. The patch is tested on PowerVM
>> and KVM machines with single and multi-function devices, and on the
>> devices behind a switch. The unplug of the affected devices post EEH
>> removal is also working fine as expected.
>>
>> Signed-off-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
>> References: d2b0f6f77ee5 ("powerpc/eeh: No hotplug on permanently 
>> removed dev")
>> ---
>>   arch/powerpc/kernel/rtas_pci.c |    6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/arch/powerpc/kernel/rtas_pci.c b/arch/powerpc/kernel/ 
>> rtas_pci.c
>> index fccf96e897f6..ce24b18712ca 100644
>> --- a/arch/powerpc/kernel/rtas_pci.c
>> +++ b/arch/powerpc/kernel/rtas_pci.c
>> @@ -57,6 +57,9 @@ int rtas_pci_dn_read_config(struct pci_dn *pdn, int 
>> where, int size, u32 *val)
>>       if (pdn->edev && pdn->edev->pe &&
>>           (pdn->edev->pe->state & EEH_PE_CFG_BLOCKED))
>>           return PCIBIOS_SET_FAILED;
>> +
>> +    if (pdn->edev && pdn->edev->mode & EEH_DEV_REMOVED)
>> +        return PCIBIOS_SET_FAILED;
>>   #endif
>>       addr = rtas_config_addr(pdn->busno, pdn->devfn, where);
>> @@ -108,6 +111,9 @@ int rtas_pci_dn_write_config(struct pci_dn *pdn, 
>> int where, int size, u32 val)
>>       if (pdn->edev && pdn->edev->pe &&
>>           (pdn->edev->pe->state & EEH_PE_CFG_BLOCKED))
>>           return PCIBIOS_SET_FAILED;
>> +
>> +    if (pdn->edev && pdn->edev->mode & EEH_DEV_REMOVED)
>> +        return PCIBIOS_SET_FAILED;
>>   #endif
>>       addr = rtas_config_addr(pdn->busno, pdn->devfn, where);
>>
>>
>