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xen/timer: make xen timer optional
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Authored by ehem_freebsd_m5p.com on Mar 3 2021, 4:33 PM.

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Summary

The timer is not used on ARM.

Adapted-to-HEAD-by: Elliott Mitchell <ehem+freebsd@m5p.com>

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R10 FreeBSD src repository
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Event Timeline

Some minor comments.

sys/amd64/conf/GENERIC
383–384

I don't think XENHVM strictly depends on xentimer (as it does on xenpci). It's the other way around, xentimer depends on XENHVM, but you should be able to build a kernel with XENHVM but without xentimer.

386

Could you please append a comment with 'Xen x86 PV timer device' , like it's done for the other lines?

Getting one of the adjustments in.

The one comment is done. Thinking about the wording for the other a bit more. The comment came from Julien Grall's original patch, so I can believe time having changed things or the original thinking being mistaken.

sys/amd64/conf/GENERIC
383–384

I don't think XENHVM strictly depends on xentimer (as it does on xenpci). It's the other way around, xentimer depends on XENHVM, but you should be able to build a kernel with XENHVM but without xentimer.

Could I have some certainty here? Does an x86 kernel built with XENHVM, but xentimer disabled boot successfully?

sys/amd64/conf/GENERIC
383–384

Yes, it will just use another timer, there are plenty on HVM guests, and on PVH it should resort to the local APIC timer.

Adjust comment along proposed line. Hopefully this language works.

This revision is now accepted and ready to land.Apr 6 2021, 9:27 AM
sys/conf/files
3552–3553

I've slightly changed this to make it depend on both xentimer and xenhvm (since trying to build the timer without the rest of xenhvm won't work anyway).

This revision was automatically updated to reflect the committed changes.