Re: [PATCH v6 01/12] PCI: liveupdate: Set up FLB handler for the PCI core

[David Matlack <dmatlack@google.com>]

On 2026-06-12 05:15 AM, Pasha Tatashin wrote:
> On Fri, 22 May 2026 20:23:59 +0000, David Matlack <dmatlack@google.com> wrote:

> > + * PCI device preservation across Live Update is built on top of the Live Update
> > + * Orchestrator's (LUO) support for file preservation across kexec. Drivers
> 
> I prefer to just use acronyms FLB, and LUO, but have links to the actual 
> documentations about them.
> 
> So, something like this:
> 
>   * :ref:`FLB <flb>` Data
>   * =====================
>   *
>   * PCI device preservation across Live Update is built on top of the
>   * :ref:`LUO <luo>` support for file preservation across kexec. Drivers
> 
> And also add _luo and _flb to Documentation/core-api/liveupdate.rst
> 
> .. _luo:
> 
>  ========================
>  Live Update Orchestrator
>  ========================
> 
> .. _flb:

Will do.

I guess I will need to add another patch to add the link references to
liveupdate.rst?

> 
>  LUO File Lifecycle Bound Global Data
>  ====================================
> 
> > [ ... skip 17 lines ... ]
> > + *
> > + *  * ``pci_liveupdate_register_flb(driver_file_handler)``
> > + *  * ``pci_liveupdate_unregister_flb(driver_file_handler)``
> > + */
> > +
> > +#define pr_fmt(fmt) "PCI: liveupdate: " fmt
> 
> Nit, may be:

Did you have a suggestion here that got lost?

> 
> > +
> > +#include <linux/io.h>
> > +#include <linux/kexec_handover.h>
> > +#include <linux/kho/abi/pci.h>
> > +#include <linux/liveupdate.h>
> > +#include <linux/mutex.h>
> > +#include <linux/mm.h>
> 
> Please sort alphabetically.

Will do.

> 
> > [ ... skip 12 lines ... ]
> > +	 * future to increase the chances that there is enough room to preserve
> > +	 * devices that are not yet present on the system (e.g. VFs, hot-plugged
> > +	 * devices).
> > +	 */
> > +	for_each_pci_dev(dev)
> > +		max_nr_devices++;
> 
> I think, we want to use kho_block [1] (it is in liveupdate/next branch) 
> to allow number of supported devices to be dynamic.
> 
> To support this, we would redefine the ABI and tracking structures like 
> so:
> 
> /* include/linux/kho/abi/pci.h */
> struct pci_ser {
> 	u64 devices;      /* Phys address of the first block header of kho_block_set */
> 	u64 nr_devices;   /* Total count of active preserved devices */
> } __packed;
> 
> /* drivers/pci/liveupdate.c */
> struct pci_flb_outgoing {
> 	struct pci_ser *ser;            /* Points to the FDT/KHO-allocated ABI struct */
> 	struct kho_block_set block_set;  /* Controls the active blocks on the fly */
> };
> 
> In  __pci_liveupdate_preserve_device() , we would search for 
> and reuse any inactive  pci_dev_ser  slot first, and only call 
> kho_block_set_grow() to expand if no inactive slots are available.
> 
> In pci_liveupdate_unpreserve_device(), we would simply 
> mark the  pci_dev_ser as inactive.

Makes sense at a high level. I'll work on switching kho_block for v7 and
get back to you if I hit any issues.

> 
> >
> > diff --git a/include/linux/pci_liveupdate.h b/include/linux/pci_liveupdate.h
> > new file mode 100644
> > index 000000000000..8ec98beefcb4
> > --- /dev/null
> > +++ b/include/linux/pci_liveupdate.h
> > @@ -0,0 +1,30 @@
> > [ ... skip 24 lines ... ]
> > +static inline void pci_liveupdate_unregister_flb(struct liveupdate_file_handler *fh)
> > +{
> > +}
> > +#endif
> > +
> > +#endif /* LINUX_PCI_LIVEUPDATE_H */
> 
> [1] https://lore.kernel.org/all/20260603154402.468928-1-pasha.tatashin@soleen.com/
> 
> Preserving: In  __pci_liveupdate_preserve_device() , we would search for 
> Unpreserving: In  pci_liveupdate_unpreserve_device(), we would simply
> 
> Preserving: In  __pci_liveupdate_preserve_device() , we would search for 
> Unpreserving: In  pci_liveupdate_unpreserve_device(), we would simply 
> 
> -- 
> Pasha Tatashin <pasha.tatashin@soleen.com>