Windows 10 guests fail to boot when attempting to passthrough network card

[Rodney W. Grimes]

> I have noticed that Windows 10 guests fail to boot when attempting to pass
> through a network card. I believe I have observed this with both cxgbe
> (t580) and mlx5en cards, but only have a cxgbe to test with now. Without
> passthrough, the Windows 10 guest boots and operates normally.
> 
> FreeBSD guests (12.0-RELEASE) have no issue when booting with the cxgbe
> card passed through - I can kldload cxgbe and I get both cxl ports showing
> up in the FreeBSD guest.
> 
> I have tested this with both 12.0-RELEASE and head (13-CURRENT r347883) as
> the host OS with no change in behavior. The bhyve output is:
> Unhandled ps2 keyboard command 0x02
> Unhandled ps2 keyboard command 0x02
> Assertion failed: (error == 0), function modify_bar_registration, file
> /usr/src/usr.sbin/bhyve/pci_emul.c, line 504.
> fbuf frame buffer base: 0x943600000 [sz 16777216]
> 
> Two main suggestions from discussions at BSDCan this week were:
> - Capture pciconf -lvb from the FreeBSD guest
> - Add some printf to pci_emul.c to capture some values when there is an
> error
> 
> I've captured the above, and a lot of other relevant info, in a Google Doc
> here (too big to post directly):
> https://docs.google.com/document/d/1t-UVIO9Aq0TPUFHyo1nVscqaW1LoPuNhfLPitL8oeTs/edit?usp=sharing
> 
> `nap

To confirm what I see from looking at your data could you tell me if this
patch triggers a barf?

--- mem.c.orig  2019-05-18 20:04:26.707995000 +0000
+++ mem.c       2019-05-18 20:04:02.205119000 +0000
@@ -97,6 +97,7 @@
		return (0);
	}
	
+printf("mmio_rb_lookup: barf ENOENT");
	return (ENOENT);
 }

-- 
Rod Grimes                                                 rgrimes at freebsd.org