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

[Shannon Zhao <zhaoshenglong@huawei.com>]

On 2016/4/22 22:32, Andrew Jones wrote:
> On Fri, Mar 25, 2016 at 05:46:20PM +0800, Shannon Zhao wrote:
>> From: Shannon Zhao <shannon.zhao@linaro.org>
>>
>> Add a virtual PMU device for virt machine while use PPI 7 for PMU
>> overflow interrupt number.
>>
>> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
>> ---
>>  hw/arm/virt.c         | 31 +++++++++++++++++++++++++++++++
>>  include/hw/arm/virt.h |  2 ++
>>  include/sysemu/kvm.h  |  1 +
>>  stubs/kvm.c           |  5 +++++
>>  target-arm/kvm64.c    | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
>>  5 files changed, 90 insertions(+)
>>
>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>> index 95331a5..94c2beb 100644
>> --- a/hw/arm/virt.c
>> +++ b/hw/arm/virt.c
>> @@ -427,6 +427,35 @@ 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;
> 
> funny indentation here
> 
>> +	}
>> +
>> +        kvm_arm_pmu_create(cpu, VIRTUAL_PMU_IRQ + 16);
> 
> I think we should have a PPI(irq) ((irq) + 16) type of macro.
> 
>> +    }
>> +
>> +    irqflags = deposit32(irqflags, GIC_FDT_IRQ_PPI_CPU_START,
>> +                         GIC_FDT_IRQ_PPI_CPU_WIDTH, (1 << vbi->smp_cpus) - 1);
>> +
>> +    armcpu = ARM_CPU(qemu_get_cpu(0));
>> +    qemu_fdt_add_subnode(vbi->fdt, "/pmu");
>> +    if (arm_feature(&armcpu->env, ARM_FEATURE_V8)) {
>> +        const char compat[] = "arm,armv8-pmuv3";
>> +        qemu_fdt_setprop(vbi->fdt, "/pmu", "compatible",
>> +                         compat, sizeof(compat));
>> +        qemu_fdt_setprop_cells(vbi->fdt, "/pmu", "interrupts",
>> +                               GIC_FDT_IRQ_TYPE_PPI, VIRTUAL_PMU_IRQ, irqflags);
>> +    }
> 
> else what? I guess it's not possible to have has_pmu and !ARM_FEATURE_V8
> at the same time right now, but it seems strange to create a /pmu node,
> but then only conditionally populate it.
> 
Yeah, currently kvm only supports guest PMU for ARMv8, but maybe in the
future it will support ARMv7.

>> +}
>> +
>>  static void create_v2m(VirtBoardInfo *vbi, qemu_irq *pic)
>>  {
>>      int i;
>> @@ -1242,6 +1271,8 @@ static void machvirt_init(MachineState *machine)
>>  
>>      create_gic(vbi, pic, gic_version, vms->secure);
>>  
>> +    fdt_add_pmu_nodes(vbi);
>> +
>>      create_uart(vbi, pic, VIRT_UART, sysmem);
>>  
>>      if (vms->secure) {
>> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
>> index ecd8589..864eb49 100644
>> --- a/include/hw/arm/virt.h
>> +++ b/include/hw/arm/virt.h
>> @@ -40,6 +40,8 @@
>>  #define ARCH_TIMER_NS_EL1_IRQ 14
>>  #define ARCH_TIMER_NS_EL2_IRQ 10
>>  
>> +#define VIRTUAL_PMU_IRQ 7
> 
> Can we find a way to make this configurable? a cpu property?
> 
Of course we can. But as we are the maker of the virt machine board, we
can decide the design of the hardware. In addition, what's the purpose
for making it configurable?

>> +
>>  enum {
>>      VIRT_FLASH,
>>      VIRT_MEM,
>> diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
>> index 6695fa7..80b6cb3 100644
>> --- a/include/sysemu/kvm.h
>> +++ b/include/sysemu/kvm.h
>> @@ -514,4 +514,5 @@ int kvm_set_one_reg(CPUState *cs, uint64_t id, void *source);
>>   * Returns: 0 on success, or a negative errno on failure.
>>   */
>>  int kvm_get_one_reg(CPUState *cs, uint64_t id, void *target);
>> +void kvm_arm_pmu_create(CPUState *cs, int irq);
>>  #endif
>> diff --git a/stubs/kvm.c b/stubs/kvm.c
>> index ddd6204..58a348a 100644
>> --- a/stubs/kvm.c
>> +++ b/stubs/kvm.c
>> @@ -6,3 +6,8 @@ int kvm_arch_irqchip_create(MachineState *ms, KVMState *s)
>>  {
>>      return 0;
>>  }
>> +
>> +void kvm_arm_pmu_create(CPUState *cs, int irq)
>> +{
>> +    return;
>> +}
>> diff --git a/target-arm/kvm64.c b/target-arm/kvm64.c
>> index b364789..b97b9ef 100644
>> --- a/target-arm/kvm64.c
>> +++ b/target-arm/kvm64.c
>> @@ -382,6 +382,57 @@ static CPUWatchpoint *find_hw_watchpoint(CPUState *cpu, target_ulong addr)
>>      return NULL;
>>  }
>>  
>> +static bool kvm_arm_pmu_support_ctrl(CPUState *cs, struct kvm_device_attr *attr)
>> +{
>> +    return kvm_vcpu_ioctl(cs, KVM_HAS_DEVICE_ATTR, attr) == 0;
>> +}
>> +
>> +static void kvm_arm_pmu_init(CPUState *cs)
>> +{
>> +    int err;
>> +
>> +    struct kvm_device_attr attr = {
>> +        .group = KVM_ARM_VCPU_PMU_V3_CTRL,
>> +        .attr = KVM_ARM_VCPU_PMU_V3_INIT,
>> +        .flags = 0,
>> +    };
>> +
>> +    if (!kvm_arm_pmu_support_ctrl(cs, &attr)) {
>> +        return;
>> +    }
> 
> I don't think we need to do this check again here. kvm_arm_pmu_init is
> only called from a function that already checked for the IRQ attribute,
> and both IRQ and INIT were added to the kernel at the same time.
> 
> Actually I think we could just opencode kvm_arm_pmu_init in
> kvm_arm_pmu_create.
> 
Sure. Thanks.

-- 
Shannon