intel graphics loosing msi interrupt on subsequent starts

Hello all!

Sorry if it is already reported...

I have recently upgaded X server from 1.4  to 1.6
(ports from ~23.01.2009 -> 03.05.2009).
On the first start everything works ok (including [glx]gears).
On the second and subsequent starts everything looks working but jerky,
I need to move mouse around to get some windows redrawn,
[glx]gears print warning message about not getting vblank interrupts
and outputs something about 1-2 frames per 5 seconds.

The inspectation with vmstat -i has shown that the card generates
interrupts only during the first start of X server.

If I set hw.pci.enable_msi="0" everything is working fine (start X server
multiple times, switch consoles, [glx]gears, number of irq16-s
is increasing, ...).

I can't be sure it is only due to X upgrade,
I have upgraded the base system also (~2 weeks old CURRENT -> 03.05.2009).

Some quick to gather system details:

~> uname -a
FreeBSD wep4035 8.0-CURRENT FreeBSD 8.0-CURRENT #0: Sun May  3 03:04:41 CEST 2009     root_at_wep4035:/usr/obj/usr/src/sys/GENERIC  amd64 
(4 GB of RAM, Core2Duo, if it matters)

>From pciconf -lv:
vgapci0_at_pci0:0:2:0:     class=0x030000 card=0x82761043 chip=0x29c28086 rev=0x02 hdr=0x00
    vendor     = 'Intel Corporation'
    device     = '(Bearlake) Integrated Graphics Controller'
    class      = display
    subclass   = VGA

>From dmesg with hw.pci.enable_msi="0":
vgapci0: <VGA-compatible display> port 0xbc00-0xbc07 mem 0xfe980000-0xfe9fffff,0xd0000000-0xdfffffff,0xfe800000-0xfe8fffff irq 16 at device 2.0 on pci0
agp0: <Intel G33 SVGA controller> on vgapci0
agp0: detected 7164k stolen memory
agp0: aperture size is 256M
drm0: <Intel G33> on vgapci0
vgapci0: child drm0 requested pci_enable_busmaster
info: [drm] AGP at 0xd0000000 256MB
info: [drm] Initialized i915 1.6.0 20080730

>From dmesg with default settings:
vgapci0: <VGA-compatible display> port 0xbc00-0xbc07 mem 0xfe980000-0xfe9fffff,0xd0000000-0xdfffffff,0xfe800000-0xfe8fffff irq 16 at device 2.0 on pci0
agp0: <Intel G33 SVGA controller> on vgapci0
agp0: detected 7164k stolen memory
agp0: aperture size is 256M
drm0: <Intel G33> on vgapci0
info: [drm] MSI enabled 1 message(s)
vgapci0: child drm0 requested pci_enable_busmaster
info: [drm] AGP at 0xd0000000 256MB
info: [drm] Initialized i915 1.6.0 20080730

Thanks,
Alexey.