Re: [PATCH 2/3] hw/arm/virt: Move kvm pmu setup to virt_cpu_post_init

[Andrew Jones]

On Tue, Jul 21, 2020 at 11:02:30AM +0100, Peter Maydell wrote:
> On Sat, 11 Jul 2020 at 11:10, Andrew Jones <drjones@redhat.com> wrote:
> >
> > Move the KVM PMU setup part of fdt_add_pmu_nodes() to
> > virt_cpu_post_init(), which is a more appropriate location. Now
> > fdt_add_pmu_nodes() is also named more appropriately, because it
> > no longer does anything but fdt node creation.
> >
> > No functional change intended.
> >
> > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > ---
> >  hw/arm/virt.c | 33 +++++++++++++++------------------
> >  1 file changed, 15 insertions(+), 18 deletions(-)
> >
> > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > index cb2fa99b1ef5..63ef530933e5 100644
> > --- a/hw/arm/virt.c
> > +++ b/hw/arm/virt.c
> > @@ -521,30 +521,15 @@ static void fdt_add_gic_node(VirtMachineState *vms)
> >
> >  static void fdt_add_pmu_nodes(const VirtMachineState *vms)
> >  {
> > -    CPUState *cpu;
> > -    ARMCPU *armcpu;
> > +    ARMCPU *armcpu = ARM_CPU(first_cpu);
> >      uint32_t irqflags = GIC_FDT_IRQ_FLAGS_LEVEL_HI;
> >
> > -    CPU_FOREACH(cpu) {
> > -        armcpu = ARM_CPU(cpu);
> > -        if (!arm_feature(&armcpu->env, ARM_FEATURE_PMU)) {
> > -            return;
> > -        }
> 
> So previously we would say "if the CPU doesn't actually have
> a PMU, don't put the PMU nodes in the FDT", but in the new logic
> it looks like we put the PMU nodes in the FDT unconditionally ?

Ah, an unintentional change in this patch with no intended changes.
How about adding something like this to the top of fdt_add_pmu_nodes()

    if (!arm_feature(&armcpu->env, ARM_FEATURE_PMU)) {
        assert(!object_property_get_bool(OBJECT(armcpu), "pmu", NULL));
        return;
    }

where the assert is optional - it just mirrors the consistency check in
virt_cpu_post_init()

Thanks,
drew

> 
> > -        if (kvm_enabled()) {
> > -            if (kvm_irqchip_in_kernel()) {
> > -                kvm_arm_pmu_set_irq(cpu, PPI(VIRTUAL_PMU_IRQ));
> > -            }
> > -            kvm_arm_pmu_init(cpu);
> > -        }
> > -    }
> > -
> >      if (vms->gic_version == VIRT_GIC_VERSION_2) {
> >          irqflags = deposit32(irqflags, GIC_FDT_IRQ_PPI_CPU_START,
> >                               GIC_FDT_IRQ_PPI_CPU_WIDTH,
> >                               (1 << vms->smp_cpus) - 1);
> >      }
> >
> > -    armcpu = ARM_CPU(qemu_get_cpu(0));
> >      qemu_fdt_add_subnode(vms->fdt, "/pmu");
> >      if (arm_feature(&armcpu->env, ARM_FEATURE_V8)) {
> >          const char compat[] = "arm,armv8-pmuv3";
> > @@ -1678,11 +1663,23 @@ static void finalize_gic_version(VirtMachineState 
> > *vms)
> >   */
> >  static void virt_cpu_post_init(VirtMachineState *vms)
> >  {
> > -    bool aarch64;
> > +    bool aarch64, pmu;
> > +    CPUState *cpu;
> >
> >      aarch64 = object_property_get_bool(OBJECT(first_cpu), "aarch64", NULL);
> > +    pmu = object_property_get_bool(OBJECT(first_cpu), "pmu", NULL);
> >
> > -    if (!kvm_enabled()) {
> > +    if (kvm_enabled()) {
> > +        CPU_FOREACH(cpu) {
> > +            if (pmu) {
> > +                assert(arm_feature(&ARM_CPU(cpu)->env, ARM_FEATURE_PMU));
> > +                if (kvm_irqchip_in_kernel()) {
> > +                    kvm_arm_pmu_set_irq(cpu, PPI(VIRTUAL_PMU_IRQ));
> > +                }
> > +                kvm_arm_pmu_init(cpu);
> > +            }
> > +        }
> > +    } else {
> >          if (aarch64 && vms->highmem) {
> >              int requested_pa_size = 64 - clz64(vms->highest_gpa);
> >              int pamax = arm_pamax(ARM_CPU(first_cpu));
> 
> thanks
> -- PMM
>