Re: [PATCH rc] PCI: Fix nested pci_dev_reset_iommu_prepare/done()

[Nicolin Chen]

On Thu, Mar 19, 2026 at 02:22:39AM +0000, Tian, Kevin wrote:
> > From: Nicolin Chen <nicolinc@xxxxxxxxxx>
> > Sent: Thursday, March 19, 2026 6:00 AM
> > 
> > Shuai found that cxl_reset_bus_function() calls pci_reset_bus_function()
> > internally while both are calling pci_dev_reset_iommu_prepare/done().
> > 
> > This results in a nested pci_dev_reset_iommu_prepare/done() call:
> >     cxl_reset_bus_function():
> >         pci_dev_reset_iommu_prepare(); // outer
> >         pci_reset_bus_function():
> >             pci_dev_reset_iommu_prepare(); // inner (re-entry)
> >             ...
> >             pci_dev_reset_iommu_done(); // inner
> >         pci_dev_reset_iommu_done(); // outer
> > 
> > However, pci_dev_reset_iommu_prepare() doesn't allow a re-entry for now.
> > 
> > Digging further, I found that most functions in pci_dev_specific_reset()
> > except reset_ivb_igd() are calling pcie_flr() that has nested those two
> > functions as well.
> > 
> > Drop the outer callbacks in:
> >  - cxl_reset_bus_function()
> >  - pci_dev_specific_reset()
> > 
> > Replace with adding the callbacks in:
> >  + reset_ivb_igd()
> > 
> 
> I wonder whether it's cleaner to just make pci_dev_reset_iommu_prepare()
> reentrant here.
> 
> what this patch does requires additional attention on specific reset functions.
> 
> e.g. reset_hinic_vf_dev() has a special logic waiting for firmware reset
> done after calling pcie_flr(). With this patch the _done() notification will
> be triggered earlier than expectation.

!

> the original way is more maintainable with prepare/done equipped in
> the highest level reset helpers in pci_reset_fn_methods[].

Yes. I agree. I will add a reset_cnt and allow re-entry.

> btw the AI review tool gave a comment:
> 
> https://sashiko.dev/#/patchset/20260318220028.1146905-1-nicolinc%40nvidia.com

My browsers on both Linux and Windows blocked this site :-/

> it won't hold if my proposal is agreed. But it still applies to your quarantine
> series which relies on accurate report of success reset.

Would you mind posting it here, if it's not too long?

Thanks
Nicolin