Re: [PATCH v3 00/66] KVM: arm64: ARMv8.3/8.4 Nested Virtualization support

Haibo Xu
2021-01-12T08:03:54Z

On Mon, 11 Jan 2021 at 16:59, Marc Zyngier <maz@kernel.org> wrote:
>
> Hi Haibo,
>
> On 2021-01-11 07:20, Haibo Xu wrote:
> > On Fri, 11 Dec 2020 at 00:00, Marc Zyngier <maz@kernel.org> wrote:
> >>
> >> This is a rework of the NV series that I posted 10 months ago[1], as a
> >> lot of the KVM code has changed since, and the series apply anymore
> >> (not that anybody really cares as the the HW is, as usual, made of
> >> unobtainium...).
> >>
> >> From the previous version:
> >>
> >> - Integration with the new page-table code
> >> - New exception injection code
> >> - No more messing with the nVHE code
> >> - No AArch32!!!!
> >> - Rebased on v5.10-rc4 + kvmarm/next for 5.11
> >>
> >> From a functionality perspective, you can expect a L2 guest to work,
> >> but don't even think of L3, as we only partially emulate the
> >> ARMv8.{3,4}-NV extensions themselves. Same thing for vgic, debug, PMU,
> >> as well as anything that would require a Stage-1 PTW. What we want to
> >> achieve is that with NV disabled, there is no performance overhead and
> >> no regression.
> >>
> >> The series is roughly divided in 5 parts: exception handling, memory
> >> virtualization, interrupts and timers for ARMv8.3, followed by the
> >> ARMv8.4 support. There are of course some dependencies, but you'll
> >> hopefully get the gist of it.
> >>
> >> For the most courageous of you, I've put out a branch[2]. Of course,
> >> you'll need some userspace. Andre maintains a hacked version of
> >> kvmtool[3] that takes a --nested option, allowing the guest to be
> >> started at EL2. You can run the whole stack in the Foundation
> >> model. Don't be in a hurry ;-).
> >>
> >
> > Hi Marc,
> >
> > I got a kernel BUG message when booting the L2 guest kernel with the
> > kvmtool on a FVP setup.
> > Could you help have a look about the BUG message as well as my
> > environment configuration?
> > I think It probably caused by some local configurations of the FVP
> > setup.
>
> No, this is likely a bug in your L1 guest, which was fixed in -rc3:
>
> 2a5f1b67ec57 ("KVM: arm64: Don't access PMCR_EL0 when no PMU is
> available")
>
> and was found in the exact same circumstances. Alternatively, and if
> you don't want to change your L1 guest, you can just pass the --pmu
> option to kvmtool when starting the L1 guest.

After passing --pmu when starting a L1 guest, I can successfully run a
L2 guest now!
Thanks so much for the help!

Haibo

>
> Hope this helps,
>
> M.
> --
> Jazz is not dead. It just smells funny...