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Re: [PATCH v3 4/4] spapr: Forbid nested KVM-HV in pre-power9 compat mode
From: |
Greg Kurz |
Subject: |
Re: [PATCH v3 4/4] spapr: Forbid nested KVM-HV in pre-power9 compat mode |
Date: |
Mon, 15 Jun 2020 11:20:31 +0200 |
On Sat, 13 Jun 2020 17:18:04 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:
> On Thu, Jun 11, 2020 at 03:40:33PM +0200, Greg Kurz wrote:
> > Nested KVM-HV only works on POWER9.
> >
> > Signed-off-by: Greg Kurz <groug@kaod.org>
> > Reviewed-by: Laurent Vivier <lvivier@redhat.com>
>
> Hrm. I have mixed feelings about this. It does bring forward an
> error that we'd otherwise only discover when we try to load the kvm
> module in the guest.
>
> On the other hand, it's kind of a layering violation - really it's
> KVM's business to report what it can and can't do, rather than having
> qemu anticipate it.
>
Agreed and it seems that we can probably get KVM to report that
already. I'll have closer look.
> Allowing POWER8 compat for an L2 is something we hope to have in the
> fairly near future.
Ok but I guess we don't want to start an L2 in compat POWER8 mode
with cap-nested-hv=on, do we ?
> Allowing POWER8 compat for L1, which is what this
> covers, is, I'll admit, likely to never happen.
>
>
> > ---
> > HW/ppc/spapr_caps.c | 10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> > index 27cf2b38af27..dfe3b419daaa 100644
> > --- a/hw/ppc/spapr_caps.c
> > +++ b/hw/ppc/spapr_caps.c
> > @@ -391,6 +391,8 @@ static void cap_nested_kvm_hv_apply(SpaprMachineState
> > *spapr,
> > uint8_t val, Error **errp)
> > {
> > ERRP_AUTO_PROPAGATE();
> > + PowerPCCPU *cpu = POWERPC_CPU(first_cpu);
> > +
> > if (!val) {
> > /* capability disabled by default */
> > return;
> > @@ -400,6 +402,14 @@ static void cap_nested_kvm_hv_apply(SpaprMachineState
> > *spapr,
> > error_setg(errp, "No Nested KVM-HV support in TCG");
> > error_append_hint(errp, "Try appending -machine
> > cap-nested-hv=off\n");
> > } else if (kvm_enabled()) {
> > + if (!ppc_check_compat(cpu, CPU_POWERPC_LOGICAL_3_00, 0,
> > + spapr->max_compat_pvr)) {
> > + error_setg(errp, "Nested KVM-HV only supported on POWER9");
> > + error_append_hint(errp,
> > + "Try appending -machine
> > max-cpu-compat=power9\n");
> > + return;
> > + }
> > +
> > if (!kvmppc_has_cap_nested_kvm_hv()) {
> > error_setg(errp,
> > "KVM implementation does not support Nested
> > KVM-HV");
> >
> >
>
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- Re: [PATCH v3 1/4] spapr: Simplify some warning printing paths in spapr_caps.c, (continued)