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Created attachment 1191885[details]
unknown device in windows guest
Description of problem:
In RHEL7.3,fw_cfg device can be shown in windows guest with no driver installed which will lead to win2016 svvp test fail.
RHEL7.2 qemu(qemu-kvm-rhev-2.3.0-31.el7.x86_64.) does not hit this issue.
As it's too late to create such driver in rhel7.3,we hope qemu can create a flag that can be used to hide the fw_cfg device in windows guest.
Version-Release number of selected component (if applicable):
qemu-kvm-rhev-2.6.0-21.el7.x86_64
How reproducible:
100%
Steps to Reproduce:
1.boot a windows server 2016 guest on rhel7.3
2.check in qtree
(qemu) info qtree
dev: fw_cfg_io, id ""
iobase = 1296 (0x510)
dma_iobase = 1300 (0x514)
dma_enabled = true
3.check in windows guest
in device manager(View-->resources by type),there is an unknown device(please check the screenshot)
Actual results:
There is an unknown device(please check the screenshot);
When we run rhel7.3 svvp test with windows2016,it will automatically detect this device has no driver installed which will lead to svvp test fail.
So I set test blocker keyword in this bug.
Expected results:
No unknown device shown in windows guest.
Additional info:
Following is Marcel's suggestion: https://bugzilla.redhat.com/show_bug.cgi?id=1246993#c14
I have some answers:
The problem is not connected to the "dma-enabled" flag, but with a new feature
added to the fw_cfg device: The possibility to see the fw_cfg data in the guest OS.
The way they did it is by adding a node in the ACPI DSDT table for the fw_cfg device:
Please see: https://lists.gnu.org/archive/html/qemu-devel/2016-02/msg04660.html
for details.
The way it is used in guest kernel can be seen here:
https://lkml.org/lkml/2016/1/27/1650
I can confirm this is the issue, possible solutions are:
- Add a Windows driver for it
- Find a way to hide the device, by removing it from DSDT or using a
an ACPI 'trick' to hide it from Windows guests - all that based on some property flag.
I suggest to reply to the QEMU upstream thread and explain what is the exact issue for Windows guests asking for guidance.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://rhn.redhat.com/errata/RHBA-2016-2673.html