On Mon, 04 Aug 2025 15:41:48 +0100,
Alexandru Elisei <alexandru.elisei@xxxxxxx> wrote:
>
> Hi Andre,
>
> On Tue, Jul 29, 2025 at 10:57:41AM +0100, Andre Przywara wrote:
> > The ARMv8.3 architecture update includes support for nested
> > virtualization. Allow the user to specify "--nested" to start a guest in
> > (virtual) EL2 instead of EL1.
> > This will also change the PSCI conduit from HVC to SMC in the device
> > tree.
> >
> > Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> > ---
> > arm64/fdt.c | 5 ++++-
> > arm64/include/kvm/kvm-config-arch.h | 5 ++++-
> > arm64/kvm-cpu.c | 12 +++++++++++-
> > 3 files changed, 19 insertions(+), 3 deletions(-)
> >
> > diff --git a/arm64/fdt.c b/arm64/fdt.c
> > index df7775876..98f1dd9d4 100644
> > --- a/arm64/fdt.c
> > +++ b/arm64/fdt.c
> > @@ -205,7 +205,10 @@ static int setup_fdt(struct kvm *kvm)
> > _FDT(fdt_property_string(fdt, "compatible", "arm,psci"));
> > fns = &psci_0_1_fns;
> > }
> > - _FDT(fdt_property_string(fdt, "method", "hvc"));
> > + if (kvm->cfg.arch.nested_virt)
> > + _FDT(fdt_property_string(fdt, "method", "smc"));
> > + else
> > + _FDT(fdt_property_string(fdt, "method", "hvc"));
> > _FDT(fdt_property_cell(fdt, "cpu_suspend", fns->cpu_suspend));
> > _FDT(fdt_property_cell(fdt, "cpu_off", fns->cpu_off));
> > _FDT(fdt_property_cell(fdt, "cpu_on", fns->cpu_on));
> > diff --git a/arm64/include/kvm/kvm-config-arch.h b/arm64/include/kvm/kvm-config-arch.h
> > index ee031f010..a1dac28e6 100644
> > --- a/arm64/include/kvm/kvm-config-arch.h
> > +++ b/arm64/include/kvm/kvm-config-arch.h
> > @@ -10,6 +10,7 @@ struct kvm_config_arch {
> > bool aarch32_guest;
> > bool has_pmuv3;
> > bool mte_disabled;
> > + bool nested_virt;
> > u64 kaslr_seed;
> > enum irqchip_type irqchip;
> > u64 fw_addr;
> > @@ -57,6 +58,8 @@ int sve_vl_parser(const struct option *opt, const char *arg, int unset);
> > "Type of interrupt controller to emulate in the guest", \
> > irqchip_parser, NULL), \
> > OPT_U64('\0', "firmware-address", &(cfg)->fw_addr, \
> > - "Address where firmware should be loaded"),
> > + "Address where firmware should be loaded"), \
> > + OPT_BOOLEAN('\0', "nested", &(cfg)->nested_virt, \
>
> --nested sounds a bit vague (what if KVM decides to nest something else in the
> future?) and the variable that keeps track of the parameter is called
> 'nested_virt'. Is it too late to rename --nested to --nested-virt for
> consistency and better clarity?
I disagree. 'nested' is pretty much unambiguous in the context of
virtualisation. 'nested-virt' is only an overstatement of an idiom
that anyone playing with kvmtool will understand.
M.
--
Jazz isn't dead. It just smells funny.
