On 6/4/26 10:17 PM, Konstantin Shkolnyy wrote:
> Signed-off-by: Konstantin Shkolnyy <[email protected]>
Commit message needs something here -- You don't need to include the
explanation of the structure (that's in the commit itself) but maybe
describe the context (e.g. you're adding the comment because you just
moved most of the contents of the structure out in support of migration
and are now describing the remaining purpose)
> ---
> include/hw/s390x/s390-pci-bus.h | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/include/hw/s390x/s390-pci-bus.h b/include/hw/s390x/s390-pci-bus.h
> index e3cbee2695..2fab28e6e0 100644
> --- a/include/hw/s390x/s390-pci-bus.h
> +++ b/include/hw/s390x/s390-pci-bus.h
> @@ -271,6 +271,14 @@ typedef struct S390PCIDMACount {
> QTAILQ_ENTRY(S390PCIDMACount) link;
> } S390PCIDMACount;
>
> +/*
> + * This structure holds the PCI device AddressSpace that QEMU needs to link
> + * into its internal structures before the zPCI and PCI devices are fully
> + * initialized. It's a QEMU requirement to provide this "root" AddressSpace
> + * early. The AddressSpace is only actually used for I/O while the PCI
> + * device is plugged in and configured by the guest, at which time it gets
> + * additional memory subregions from zPCI device, that can do real work.
> + */
To be more clear, it's not that it is required 'early' so much as that
it is required to be there at the time the PCI device is plugged.
The lifecycle has always been a bit odd here; it is an attribute of the
zPCI device, but is required by the PCI device in order to function and
the necessary linkage between the 2 (PCI->zPCI) is established via the
iommu_table in the S390pciState. Would be good to work some of that
into this explanation.
> struct S390PCIIOMMU {
> Object parent_obj;
> AddressSpace as;
