On 08/11/17 01:31, Aleksandr Bezzubikov wrote: > +PCIE-PCI bridge hot-plug > +======================= > +Guest OSes require extra efforts to enable PCIE-PCI bridge hot-plug. > +Motivation - now on init any PCI Express root port which doesn't have > +any device plugged in, has no free buses reserved to provide any of them > +to a hot-plugged devices in future. > + > +To solve this problem we reserve additional buses on a firmware level. > +Currently only SeaBIOS is supported. > +The way of bus number to reserve delivery is special > +Red Hat vendor-specific PCI capability, added to the root port > +that is planned to have PCIE-PCI bridge hot-plugged in. > + > +Capability layout (defined in include/hw/pci/pci_bridge.h): > + > + uint8_t id; Standard PCI capability header field > + uint8_t next; Standard PCI capability header field > + uint8_t len; Standard PCI vendor-specific capability header field > + > + uint8_t type; Red Hat vendor-specific capability type > + List of currently existing types: > + RESOURCE_RESERVE = 1 > + > + > + uint32_t bus_res; Minimum number of buses to reserve > + > + uint64_t io; IO space to reserve > + uint32_t mem Non-prefetchable memory to reserve > + > + This two fields are mutually exclusive:
[*] mark this > + uint32_t mem_pref_32; Prefetchable memory to reserve (32-bit MMIO) > + uint64_t mem_pref_64; Prefetchable memory to reserve (64-bit MMIO) > + > +If any reservation field is -1 then this kind of reservation is not > +needed and must be ignored by firmware. > + > +mem_pref_* fields mutual exclusiveness means they cannot be -1 both. Please drop the last sentence; it is perfectly possible that a bridge doesn't need either 32-bit or 64-bit prefetchable MMIO reservation. "Mutually exclusive" usually means "at most one", not "exactly one". (E.g., think of the "mutex" construct -- in the critical section being protected by the mutex, there can be Thread 1, Thread 2, or none of them.) So, beyond dropping the last sentence, I suggest to replace the one marked with [*] with the following, for clarity: At most one of the following two fields may be set to a value different from -1: With this update, for this patch: Reviewed-by: Laszlo Ersek <ler...@redhat.com> Thanks! Laszlo