Brandon Bergren <> changed:

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--- Comment #2 from Brandon Bergren <> ---
Created attachment 187571
VMM patch (from HardenedBSD)

This affects me too.

HardenedBSD has the most elegant fix at
-- I have attached a copy of the patch. I can confirm that with just that patch
I can successfully run OpenBSD 6.1 in bhyve on my machine that is otherwise
affected by this problem.

I believe it makes a lot more sense than emulating the MSR (i.e. what

My SuperMicro C7Z170-OCE board actually has bios options for enabling and
disabling the silicon debug status and lock bit, so if I were to misconfigure
my bios, the countermeasure would have actually been effective (when applied to
the host).

I can verify though that with it disabled in the bios, it is indeed locked
down, without needing the countermeasure.
root@narwhal:~ # kldload cpuctl
root@narwhal:~ # cpucontrol -m 0xc80 /dev/cpuctl0
MSR 0xc80: 0x00000000 0x40000000

I still think the countermeasure is a good idea though!
is a version of the countermeasure that checks the virtualization flag too so
it will avoid tickling the bhyve limitation while still providing protection.

But at the very least, filter the SDBG feature flag.

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