How to properly resize VG/LV on LVM?

[Bartosz Maciejewski <bartosz%maciejewski.org@localhost>]

Hello there,

I got logical volume for mailboxes on LVM for easy expanding as 
mailboxes are growing. However I can't really resize it, or I don't know 
how to do it on NetBSD.

Filesystem                            Size       Used Avail %Cap Mounted on
/dev/mapper/varmailvg-virtuallv       984G       860G 74G  92% 
/var/mail/virtual

I already extended disk on Xen Level from 1000GB to 1200GB, and dmesg is 
showing it correctly:

xbd3 at xenbus0 id 51776: Xen Virtual Block Device Interface
xbd3: using event channel 11
xbd3: 1200 GB, 512 bytes/sect x 2516582400 sectors
xbd3: WARNING: cache flush not supported by backend

Then I run:

# lvm pvresize /dev/rxbd3a
  Physical volume "/dev/rxbd3a" changed
  1 physical volume(s) resized / 0 physical volume(s) not resized

which looks good, but lvm pvs still shows 1000GB instead of 1200GB

# lvm pvs
  PV          VG        Fmt  Attr PSize    PFree
  /dev/rxbd3a varmailvg lvm2 a-   1000.00g 1020.00m

Probably I should "resize in place" with disklabel or fstab after 
extending in Xen but I don't know exactly how. There is also resize_ffs 
somewhere in a process I think.

Is there any guide for NetBSD how to properly extend lvm volume?