2016-04-26 19:26+0000, Cao, Lei:
> Updates to KVM API documentation
> ---
I have five broad questions about design of the interface:
* Why are IOCTLs marked with "Called once when entering live
migration/checkpoint mode" separate from KVM_INIT_MT?
* Is there a reason to call KVM_ENABLE_MT often?
* How significant is the benefit of MT_FETCH_WAIT?
* When would you disable MT_FETCH_REARM?
* What drawbacks had an interface without explicit checkpointing cycles?
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> @@ -3120,6 +3120,176 @@ struct kvm_reinject_control {
A bit to the code itself:
> +4.99 KVM_INIT_MT
> +
> +Capability: basic
"basic" ioctls were present since the first version of KVM.
We can't change the past, so please add a new capability.
> +4.102 KVM_MT_SUBLIST_FETCH
> +
> +Capability: basic
> +Architectures: x86
> +Type: vm ioctl
> +Parameters: struct mt_sublist_fetch_info (in/out)
> +Returns: 0 on success, -1 on error
> +
> +/* for KVM_MT_SUBLIST_FETCH */
> +struct mt_gfn_list {
> + __s32 count;
> + __u32 max_dirty;
> + __u64 *gfnlist;
gfn (= gpa >> PAGE_SHIFT) is not enough to specify a page for userspace,
because KVM has a concept of address spaces and pages from multiple
slots can be mapped into the same gfn (e.g. x86 SMRAM).
Providing a memslot/offset pair seems best. (I'd start by addressing
Kai's comment on [3/6] about binding gfnlist to memslots.)
Thanks.
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