[Libre-soc-dev] [OpenPOWER-HDL-Cores] https://bugzilla.kernel.org/show_bug.cgi?id=213257

[Paul Mackerras]

On Fri, May 28, 2021 at 12:51:35PM +0100, Luke Kenneth Casson Leighton wrote:
> not sure where this might best else be sent.
> 
> Lauri has written a mini kvm runner for ppc64 with the intention to
> allow single-step execution where a memory dump and full register dump
> may be carried out after every single instruction.  it manages around
> 35k instructions per second this way.

Sounds very odd.  Some more details would be helpful.  What sort of
machine are you running this on?  Are you using the kvm-hv module or
the kvm-pr module?  The architecture doesn't provide any way for
hypervisor mode to single-step supervisor-mode code, so kvm-hv, which
exploits hypervisor mode, doesn't support guest single-step.  The
other variant, kvm-pr, runs the entire guest in user mode, using
trap-and-emulate to handle all privileged instructions, so it is quite
slow, only supports HPT translation, is not much used and not well
maintained.

Paul.