On 07/06/2016 18:34, Dr. David Alan Gilbert wrote: > * Paolo Bonzini (pbonz...@redhat.com) wrote: >> >> >> On 07/06/2016 16:43, Dr. David Alan Gilbert wrote: >>> b) I think you should really try and split it into two parts: >>> 1) A VMSTATE_ARRAY_CUSTOM (?) - so it's an array of elements but we've >>> got a special >>> way of allocating/counting/reading the elements >>> 2) A version of that which is for a QTAILQ. >>> It's important that whatever ends up on the migration stream doesn't >>> reflect >>> that it happens to be implemented as a QTAILQ; so if you decide to >>> change >>> it later the migration compatibility doesn't break. >> >> (Just to clarify before Jianjun wakes up) a VMSTATE_ARRAY is just a >> sequence of elements. The count, if needed as in a VARRAY, is stored >> earlier and separately. Currently lists (including this QTAILQ) are >> usually represented in the migration stream as a sequence of elements >> preceded by "1" and terminated by a "0". Would you like to change it to >> a count + sequence as well? >> >> This would prevent using the new QTAILQ support for other existing lists >> such as virtio-blk and scsi's request lists. > > That depends if it's something you're trying to keep migration compatibility > with; if you're trying to keep format compaibility then sure keep it as is. > If you're not trying to keep compatibility, then why can't virtio-blk or > scsi request lists also use a count rather than the markers?
We're trying to keep compatibility, and I think it's among the last bits that are resisting conversion to vmstate. Which explains my interest in Jianjun's patches. :) Paolo >>> c) Use new trace_ names for get_qtailq rather than misusing >>> trace_vmstate_load_state* >>> d) Add a trace_ for put_qtailq as well - that way when it goes horribly >>> wrong we can >>> turn the tracing on on both sides :-) >>> e) Is there anyway to make QTAILQ_RAW_INSERT_TAIL any more readable? >>> I don't think I understand why you can't use the standard QTAILQ >>> macros. >> >> Because they assume a particular type. The "raw" version need to work on >> void*. > > Ah OK. > > Dave > >> >> Thanks, >> >> Paolo >> >>> f) You might need to fix up Amit's scripts/vmstate-static-checker.py > -- > Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK >
