Re: annual howto rampage

[Greg Troxel <gdt%lexort.com@localhost>]

Thanks for the detailed reply to my queries.  I have applied your
comments to the howto, and when that was straightforward I have pruned
the reply below.

Manuel Bouyer <bouyer%antioche.eu.org@localhost> writes:

>>   - Is the problem with i386 PV guests under 4.18 about all PV, or just
>>     NetBSD?
>
> What problem are you talking about ?
> It this is the requirement to use pvhsim, it's for all i386 PV guests

I meant "i386 pv guest does not work".  Ack, and edited.

>>   - Is it true that PVH and PVHVM both also require VT-X/SVM just like HVM?
>
> Yes, the requirements are the same as HVM

I have a machine without VT-X (yes, I know it's from 2010):

  cpu0: "Pentium(R) Dual-Core  CPU      E5700  @ 3.00GHz"
  cpu0: Intel Xeon 31xx, 33xx, 52xx, 54xx, Core 2 Quad 8xxx and 9xxx (686-class)
  cpu0: family 0x6 model 0x17 stepping 0xa (id 0x1067a)
  cpu0: features 0x1fc9cbf5<FPU,DE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MCA,CMOV,PAT>
  cpu0: features 0x1fc9cbf5<CLFSH,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT>
  cpu0: features1 0x4002201<SSE3,SSSE3,CX16,XSAVE>
  cpu0: features2 0x20100800<SYSCALL/SYSRET,XD,EM64T>
  cpu0: features3 0x1<LAHF>

It runs PV guests fine.  Interestingly, it runs a PV netbsd-9 i386 guest
as pvh/pvshim apparently fine.  But flipping a netbsd-9 amd64 guest to
pvh/pvhsim (from just pv) makes it at least 100x slow (guessing, but it
goes from normal to "did I get teleported back to a VAX 11/750 with 1 MB
of RAM that is paging constantly")?

I wonder what's going on with i386 pvshim, if it somehow doesn't provoke
the slowness.

I wonder then if trying to run pvh/hvm/pvhvm "needing" VT-X is that it
won't work at all, or that it is so painful that nobody would ever do
it.

Regarding your tests:

  I don't see PVHVM mode.  Is that because it doesn't work, or because
  you just don't, or ?

  The test code to run various modes is great howto fodder.  Is that in
  a repo I can point to?  I see I can find the anita output when it
  fails from the log, but if it works, there is only the ATF output.  It
  would be nice to link anita output always.