Re: [Qemu-devel] [PATCH v2 2/3] hw/arm/virt: Add PMU node for virt machine

[Andrew Jones]

On Mon, Apr 25, 2016 at 02:52:45PM +0800, Shannon Zhao wrote:
> 
> 
> On 2016/4/25 1:28, Andrew Jones wrote:
> > On Sat, Apr 23, 2016 at 06:04:14PM +0800, Shannon Zhao wrote:
> >> > From: Shannon Zhao <address@hidden>
> >> > 
> >> > Add a virtual PMU device for virt machine while use PPI 7 for PMU
> >> > overflow interrupt number.
> >> > 
> >> > Signed-off-by: Shannon Zhao <address@hidden>
> >> > ---
> >> >  hw/arm/virt.c         | 31 +++++++++++++++++++++++++++++++
> >> >  include/hw/arm/virt.h |  4 ++++
> >> >  include/sysemu/kvm.h  |  1 +
> >> >  stubs/kvm.c           |  5 +++++
> >> >  target-arm/kvm64.c    | 39 +++++++++++++++++++++++++++++++++++++++
> >> >  5 files changed, 80 insertions(+)
> >> > 
> >> > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> >> > index 56d35c7..d77b314 100644
> >> > --- a/hw/arm/virt.c
> >> > +++ b/hw/arm/virt.c
> >> > @@ -428,6 +428,35 @@ static void fdt_add_gic_node(VirtBoardInfo *vbi, 
> >> > int type)
> >> >      qemu_fdt_setprop_cell(vbi->fdt, "/intc", "phandle", 
> >> > vbi->gic_phandle);
> >> >  }
> >> >  
> >> > +static void fdt_add_pmu_nodes(const VirtBoardInfo *vbi)
> >> > +{
> >> > +    CPUState *cpu;
> >> > +    ARMCPU *armcpu;
> >> > +    uint32_t irqflags = GIC_FDT_IRQ_FLAGS_LEVEL_HI;
> >> > +
> >> > +    CPU_FOREACH(cpu) {
> >> > +        armcpu = ARM_CPU(cpu);
> >> > +        if (!armcpu->has_pmu) {
> >> > +            return;
> >> > +        }
> >> > +
> >> > +        kvm_arm_pmu_create(cpu, PPI(VIRTUAL_PMU_IRQ));
> >> > +    }
> >> > +
> >> > +    irqflags = deposit32(irqflags, GIC_FDT_IRQ_PPI_CPU_START,
> >> > +                         GIC_FDT_IRQ_PPI_CPU_WIDTH, (1 << 
> >> > vbi->smp_cpus) - 1);
> > The shift will overflow when configuring a machine to have more than
> > 32 cpus. You should confirm smp_cpus is <= GIC_FDT_IRQ_PPI_CPU_WIDTH
> > before generating a mask this way, otherwise you can just pass in 0xff.
> > 
> Ah, right. So it could check the gictype like what we do in
> fdt_add_timer_nodes.

Oh, now that I look closer we definitely need that condition. Otherwise
we're losing the LEVEL_HI flag that irqflags is initialized to for no
reason.

Thanks,
drew