kern/189097: 10-STABLE breaks Windows Azure compatibility

[Barry Boone]

>Number:         189097
>Category:       kern
>Synopsis:       10-STABLE breaks Windows Azure compatibility
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Apr 29 06:00:00 UTC 2014
>Closed-Date:
>Last-Modified:
>Originator:     Barry Boone
>Release:        10-STABLE
>Organization:
Tulsa Network Solutions
>Environment:
FreeBSD freebsdazure 10.0-STABLE FreeBSD 10.0-STABLE #1 r265074M: Tue Apr 29 00:09:57 CDT 2014     boone at freebsdazure:/usr/obj/usr/src2/sys/GENERIC  amd64
>Description:
I've been testing FreeBSD 10 on the Windows Azure cloud platform, which is naturally very similar to a Hyper-V environment.

FreeBSD 10.0-Release, and 10.0p1 both work fine under Azure.  I've been able to get a modified version of the WALinuxAgent script working, and can provision the OS from the Azure interface and all seems stable and good.

During testing, I created an image with the 10-STABLE kernel.  An MFC to the stable branch, I believe revision r263065, changed the way that the driver scans for virtual IDE/SCSI devices.  The effect, is that while the main OS disk is found and mounted, the Microsoft "temporary" disk that is allocated for use as temp space and/or swap, does not get detected on bootup.

Example:

Under 10.0-RELEASE...

da0 at blkvsc0 bus 0 scbus1 target 0 lun 0
da0: <Msft Virtual Disk 1.0> Fixed Direct Access SCSI-4 device
da0: 300.000MB/s transfers
da0: Command Queueing enabled
da0: 30720MB (62914560 512 byte sectors: 255H 63S/T 3916C)
da1 at blkvsc1 bus 0 scbus2 target 1 lun 0
da1: <Msft Virtual Disk 1.0> Fixed Direct Access SCSI-4 device
da1: 300.000MB/s transfers
da1: Command Queueing enabled
da1: 61440MB (125829120 512 byte sectors: 255H 63S/T 7832C)

Under 10-STABLE, da1 (blkvsc1) is not detected at all.


>How-To-Repeat:
Compile 10-STABLE's generic kernel, make installkernel.  To get back to normal, boot the 10.0p1 release kernel.
>Fix:
In the file sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c

change the STORVSC_MAX_TARGETS value to 2.

i.e. 

#define STORVSC_MAX_TARGETS (2)

This fixed the issue for me, with this one line patch, I have 10-STABLE working perfectly on Azure again.



>Release-Note:
>Audit-Trail:
>Unformatted: