Re: [PATCH v9 09/13] PCI: liveupdate: Adopt ACS controls in incoming preserved devices

[Pranjal Shrivastava]

On Fri, Sep 18, 2026 at 08:06:35PM +0000, David Matlack wrote:
> Adopt Access Control Services (ACS) controls on all incoming preserved
> devices (endpoints and upstream bridges) during a Live Update.
> 
> Inheriting ACS flags avoids changing routing rules while memory
> transactions are in flight from preserved devices. This is also strictly
> necessary to ensure that IOMMU group assignments do not change during or
> after Live Update.
> 
> The adopted controls are recorded by the pci_save_state() call in
> pci_bus_add_device(), which runs before drivers bind, so they are
> automatically reapplied by pci_restore_state() if the device is reset.
> If that save buffer could not be allocated there is nowhere to record
> the adopted controls, and they would be silently lost by the first
> reset. Program ACS from scratch in that case, which is a better outcome
> than leaving ACS disabled.
> 
> To simplify ACS inheritance, reject preserving any devices that require
> quirks to enable ACS as those quirks would also have to take Live Update
> into account.
> 
> Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>

Reviewed-by: Pranjal Shrivastava <praan@xxxxxxxxxx>

Thanks,
Praan