Red Hat Bugzilla – Bug 799028
[RFE] Add command line option to enable bmi1 feature on AMD processors
Last modified: 2013-02-21 02:32:37 EST
Description of problem:
The bmi1 support flag is forwarded to the guest OS only if "-cpu host" is used. There is no option to enable exposing this functionality with other (compatible) cpu models.
When using qemu-kvm managed by libvirt, there's no possibility to use this feature with reasonable configurations. (Host processor passthrough cannot be used easily with migration)
Version-Release number of selected component (if applicable):
Steps to Check:
# qemu-kvm -cpu Opteron_G3,+bmi1
CPU feature bmi1 not found
Feature BMI1 cannot be exposed to guest OS without using "-cpu host".
Feature bmi1 can be enabled and exposed to guests using eg "-cpu OpteronG3,+bmi1...".
A option should be added that enables passing through CPUID fn. 0x00000007 reg EBX bit. 3 to the guest OS on compatible processors.
About bmi1 flag,would you please tell qe which amd platforms(host) includes this flag? thanks
the bmi1 flag is exposed on hosts that support the new bit manipulation instructions. This feature is included in the new Piledriver architecture from AMD.
Thanks peter,according to comment3 and comment4,set qa_ack+
verify this bug with qemu-kvm-0.12.1.2-2.334.el6.x86_64 and kernel 2.6.32-339.el6.x86_64
steps to verify:
1.boot rhel6.4 guest with -cpu Opteron_G3,+bmi1 on Seoul host
2.check flag bmil inside guest.
'bmil' flag is exposed to guest
so according to expected results in description, this bug is fixed.
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.