bhyve: [snapshot] Simplify restore kernel structs

[gusev.vitaliy_gmail.com]

Summary

Both devices and kernel structs can use the same 'lookup_dev' function instead of having duplicated code.

Sponsored by: vStack

Related to multiple devices support.

[corvink]

usr.sbin/bhyve/snapshot.c

858

Stray newline

[gusev.vitaliy_gmail.com]

Fixed note from @corvink

[jhb]

Can you provide more description of what this change is doing? From what I can tell it uses err directly to abort quicker if it fails to restore an in-kernel structure, it inlines vm_restore_kern_struct into the loop in vm_restore_kern_structs. It renames vm_snapshot_kern_structs which is somewhat gratuitous IMO as it now no longer matches the other function names like vm_snapshot_user_devs. But I think the big change is not using lookup_struct and instead using meta->dev_name instead of meta->dev_req as the main key for the JSON for a given kernel struct? I think this means you can avoid lookup_struct because now instead of a flat array of all kernel structures they are separate objects with unique names? Can you expand on that more perhaps maybe with some examples of before/after JSON snippets? I would also suggest perhaps only doing the JSON change in this commit and not mixing in the other changes that I think obscure the real change you are making (e.g. the function rename, or inlining the function).

[gusev.vitaliy_gmail.com]

In D40105#921197, @jhb wrote:

Can you provide more description of what this change is doing? From what I can tell it uses err directly to abort quicker if it fails to restore an in-kernel structure, it inlines vm_restore_kern_struct into the loop in vm_restore_kern_structs. It renames vm_snapshot_kern_structs which is somewhat gratuitous IMO as it now no longer matches the other function names like vm_snapshot_user_devs. But I think the big change is not using lookup_struct and instead using meta->dev_name instead of meta->dev_req as the main key for the JSON for a given kernel struct? I think this means you can avoid lookup_struct because now instead of a flat array of all kernel structures they are separate objects with unique names? Can you expand on that more perhaps maybe with some examples of before/after JSON snippets? I would also suggest perhaps only doing the JSON change in this commit and not mixing in the other changes that I think obscure the real change you are making (e.g. the function rename, or inlining the function).

@jhb In short:

Both devices and kernel struct can use the same 'lookup_dev' function instead of having duplicated code.

It removes vm_restore_kern_struct, lookup_struct as duplicated code.

[jhb]

Can you provide some before/after JSON snippets?

[gusev.vitaliy_gmail.com]

In D40105#923164, @jhb wrote:

Can you provide some before/after JSON snippets?

@jhb Yes, sure:

Without patch D40105:

"kern_structs": [
  {
    "debug_name": "vhpet",
    "device": 5,
    "size": 284,
    "file_offset": 0
  },
  ...

Patched with D40105:

"kern_structs": [
  {
    "device": "vhpet",
    "size": 284,
    "file_offset": 0
  },
 ...