bhyve: emulate CLFLUSH and CLFLUSHOPT.
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Authored by kib on Oct 9 2018, 2:23 PM.

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jhb
rgrimes
araujo

Group Reviewers

bhyve

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rS339331: bhyve: emulate CLFLUSH and CLFLUSHOPT.

Summary

Apparently CLFLUSH on mmio can cause VM exit, as reported in PR 232081.
I do not see that anything useful can be done except emulating page faults on invalid addresses.

Can you suggest a way to test this ?

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rS FreeBSD src repository - subversion

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Event Timeline

kib created this revision.Oct 9 2018, 2:23 PM

Herald added a reviewer: rgrimes. · View Herald TranscriptOct 9 2018, 2:23 PM

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Harbormaster completed remote builds in B20086: Diff 48932.Oct 9 2018, 2:23 PM

Looks good to me.

emaste added a subscriber: emaste.Oct 10 2018, 2:06 PM

Though this may fix running 12.0 on 12.0 we well need EN's back to 11 and perhaps even 10 as the issue exists there as well.
How badly do we need that CLFLUSH instruction in 12?

In D17482#373384, @rgrimes wrote:

Though this may fix running 12.0 on 12.0 we well need EN's back to 11 and perhaps even 10 as the issue exists there as well.

It is not about 'fixing 12 on 12'. If CLFLUSH may cause vm exit, then it needs to be emulated regardless of the FreeBSD use of CLFLUSH.
Anyway, the patch attached at the referenced PR makes FreeBSD 12 not to use CLFLUSH under virtualization, same as it was some time before.

How badly do we need that CLFLUSH instruction in 12?

I do not understand this question.

Lgtm!

This revision is now accepted and ready to land.Oct 10 2018, 4:27 PM

jhb accepted this revision.Oct 11 2018, 6:09 PM

Simplify. There is no sense in reading the first byte in the cacheline, the supplied address is good enough as well. A cacheline is always fully contained in the page which access permissions we probe.

This revision now requires review to proceed.Oct 12 2018, 12:25 PM

Harbormaster completed remote builds in B20160: Diff 49055.Oct 12 2018, 12:25 PM

This revision was not accepted when it landed; it landed in state Needs Review.Oct 12 2018, 3:30 PM

Closed by commit rS339331: bhyve: emulate CLFLUSH and CLFLUSHOPT. (authored by kib). · Explain Why

This revision was automatically updated to reflect the committed changes.