bhyve: Remove vmctx member from struct vm_snapshot_meta.

[jhb]

Summary

This is a userland-only pointer that isn't relevant to the kernel and
doesn't belong in the ioctl structure shared between userland and the
kernel. For the kernel, the old structure for the ioctl is still
supported under COMPAT_FREEBSD13.

This changes vm_snapshot_req() in libvmmapi to accept an explicit
vmctx argument.

It also changes vm_snapshot_guest2host_addr to take an explicit vmctx
argument. As part of this change, move the declaration for this
function and its wrapper macro from vmm_snapshot.h to snapshot.h as it
is a userland-only API.

[markj]

For the kernel, the old structure for the ioctl is still supported under COMPAT_FREEBSD13.

Do we really care about preserving compatibility for a feature that isn't compiled in (in userspace anyway) by default? Since you already did the work then I guess it might as well stay but it seems unnecessary.

[jhb]

In D38125#866342, @markj wrote:

For the kernel, the old structure for the ioctl is still supported under COMPAT_FREEBSD13.

Do we really care about preserving compatibility for a feature that isn't compiled in (in userspace anyway) by default? Since you already did the work then I guess it might as well stay but it seems unnecessary.

I think we probably mostly don't, but it was cheap to add.

[jhb]

Rebase