Remove support for Xen PV domU kernels. Support for HVM domU kernels remains. Xen is planning to remove support for PV upstream since it is harder to maintain and has more overhead. Modern x86 CPUs include virtualization extensions that support HVM guests instead of PV guests. In addition, the PV code was i386 only and not as well maintained recently as the HVM code.
Details
Details
- universe builds (done)
- run-time testing of HVM kernels (I don't have a Xen host setup, so would appreciate it if someone else could just boot a GENERIC kernel with this patch applied and verify it still works ok)
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Diff Detail
- Repository
- rS FreeBSD src repository - subversion
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One general note is that I haven't gone through and audited for XENHVM. Meaning, should we remove !XENHVM code in places like sys/dev/xen, or in the sys/{amd64,i386}/include/xen headers? I think we can also probably wholesale remove at least <machine/xen/xenpmap.h>. For now I'm going to do a universe build and see what breaks.
| sys/i386/include/xen/xenvar.h | ||
|---|---|---|
| 33–34 | The amd64 version of this file exposes a bit of this stuff that was only under XEN on i386. | |
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Ok, I think this is ready for the first round of reviews at least. Are there things I am missing or things I should put back?
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At least xen(4) also needs updating. Not sure if there are any other manpages to update?
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Can the pvcpu driver be removed? It claims to only be needed for PV, but was compiled in when xenhvm was enabled as well.
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Actually, should I remove anything that depend on xen_pv_domain() returning true? (E.g. the shutdown hook in the console driver)
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No, the pvcpu driver is needed for PVH support which is the mode that we use to run as Dom0.
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Ok, then I think this is ready for review. Can you double check that none of my changes (esp. in sys/dev/xen or sys/x86/xen) will break PVH? Also, can you review my changes to xen(4)? If my updates regarding HVM on i386 are correct then I may do those first as a separate commit.
| share/man/man4/xen.4 | ||
|---|---|---|
| 31 | I will. I'm never optimistic enough to expect one day turnarounds on changes, so I wait until it's ok'd and then I bump it before committing. | |
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Roger, I just updated the summary to be a candidate commit message. Please feel free to review that to ensure that it is accurate, in particular in regards to what Xen's plans are for PV going forward (I believe what I've written matches what you told me in person at BSDCan last year, but I'd like to make certain).
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I would change s/remove/phase out/ in the commit message. The Hypervisor itself is probably going to still support PV for quite some time, although the recommendation is to use PVH.
The rest looks fine to me, I've tested both a amd64/i386 guest and a PVH Dom0 and so far no problems :).