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Differential D29665

bhyve: implement rdmsr for MSR_IA32_FEATURE_CONTROL
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Authored by corvink on Apr 9 2021, 5:42 AM.
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bcran
grehan
jhb
jlduran_gmail.com
rgrimes

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grehan
jhb
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bhyve
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rG17d214c2ca9f: bhyve: implement rdmsr for MSR_IA32_FEATURE_CONTROL
Summary

Windows guest crashes on boot. It's caused by rdmsr to MSR_IA32_FEATURE_CONTROL. Windows checks this MSR to determine enabled VMX features. Bhyve hasn't implement it yet. For that reason, bhyve injects a GP which causes Windows to crash.
This patch returns MSR_IA32_FEATURE_CONTROL with Lock Bit set and VMX disabled to tell Windows that VMX isn't available.

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rG FreeBSD src repository
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Event Timeline

corvink created this revision.Apr 9 2021, 5:42 AM
Herald added subscribers: bcran, rgrimes. · View Herald TranscriptApr 9 2021, 5:42 AM
corvink requested review of this revision.Apr 9 2021, 5:42 AM
corvink edited the summary of this revision. (Show Details)
corvink retitled this revision from bhyve: fix crash of rdmsr from windows guests to bhyve: implement rdmsr for MSR_IA32_FEATURE_CONTROL.Apr 9 2021, 5:45 AM
jlduran_gmail.com added a subscriber: jlduran_gmail.com.Apr 10 2021, 3:28 PM
jlduran_gmail.com added inline comments.
usr.sbin/bhyve/xmsr.c
133

I guess machine/specialreg.h already defines IA32_FEATURE_CONTROL_LOCK?

corvink updated this revision to Diff 87295.Apr 12 2021, 5:39 AM
  • Use IA32_FEATURE_CONTROL_LOCK define
corvink marked an inline comment as done.Apr 12 2021, 5:39 AM
jhb added a subscriber: jhb.Apr 12 2021, 5:54 PM

This looks ok to me with the tweaked comment. Does this permit Windows guests to boot without -w?

usr.sbin/bhyve/xmsr.c
129–131
corvink updated this revision to Diff 87361.Apr 13 2021, 5:26 AM

I'm able to boot a Windows guest without -w by applying this patch.

corvink marked an inline comment as done.Apr 13 2021, 5:27 AM
grehan accepted this revision.Apr 13 2021, 7:51 AM
grehan added a subscriber: grehan.

Looks fine, and preserves #GP on writes.

This revision is now accepted and ready to land.Apr 13 2021, 7:51 AM
jhb accepted this revision.Apr 13 2021, 3:31 PM

Do you have this already staged as a git commit in a tree Peter or I could pull from?

corvink added a comment.Apr 14 2021, 8:48 AM

This commit isn't staged in a tree.

Closed by commit rG17d214c2ca9f: bhyve: implement rdmsr for MSR_IA32_FEATURE_CONTROL (authored by corvink, committed by grehan). · Explain WhyApr 15 2021, 5:52 AM
This revision was automatically updated to reflect the committed changes.
grehan added a commit: rG17d214c2ca9f: bhyve: implement rdmsr for MSR_IA32_FEATURE_CONTROL.

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usr.sbin/
bhyve/
8 lines

Diff 87458

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usr.sbin/bhyve/xmsr.c

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