[PATCH v7 19/19] KVM: ARM64: Add a new kvm ARM PMU device

Christoffer Dall
2015-12-18T10:00:12Z

On Thu, Dec 17, 2015 at 03:22:50PM +0800, Shannon Zhao wrote:
>
>
> On 2015/12/17 4:33, Christoffer Dall wrote:
> > On Wed, Dec 16, 2015 at 04:06:49PM +0800, Shannon Zhao wrote:
> >> Hi,
> >>
> >> On 2015/12/16 15:31, Shannon Zhao wrote:
> >>>>>>>>> But in this case, you're returning an error if it is *not* initialized.
> >>>>>>>>> I understand that in that case you cannot return an interrupt number (-1
> >>>>>>>>> would be weird), but returning -EBUSY feels even more weird.
> >>>>>>>>>
> >>>>>>>>> I'd settle for -ENOXIO, or something similar. Anyone having a better idea?
> >>>>>>>>>
> >>>>> ENXIO or ENODEV would be my choice too, and add that to the
> >>>>> Documentation clearly describing when this error code is used.
> >>>>>
> >>>>> By the way, why do you loop over all VCPUS to set the same value when
> >>>>> you can't do anything per VCPU anyway? It seems to me it's either a
> >>>>> per-VM property (that you can store on the VM data structure) or it's a
> >>>>> true per-VCPU property?
> >>> This is a per-VCPU property. PMU interrupt could be PPI or SPI. For PPI
> >>> the interrupt numbers are same for each vcpu, while for SPI they are
> >>> different, so it needs to set them separately. I planned to support both
> >>> PPI and SPI. I think I should add support for SPI at this moment and let
> >>> users (QEMU) to set these interrupts for each one.
> >>
> >> How about below vPMU Documentation?
> >>
> >> ARM Virtual Performance Monitor Unit (vPMU)
> >> ===========================================
> >>
> >> Device types supported:
> >> KVM_DEV_TYPE_ARM_PMU_V3 ARM Performance Monitor Unit v3
> >>
> >> Instantiate one PMU instance for per VCPU through this API.
> >>
> >> Groups:
> >> KVM_DEV_ARM_PMU_GRP_IRQ
> >> Attributes:
> >> The attr field of kvm_device_attr encodes two values:
> >> bits: | 63 .... 32 | 31 .... 0 |
> >> values: | vcpu_index | irq_num |
> BTW, I change this Attribute to below format and pass vcpu_index through
> this Attribute while pass irq_num through kvm_device_attr.addr.
> Is it fine?
>
> bits: | 63 .... 32 | 31 .... 0 |
> values: | reserved | vcpu_index |
>
> >> The irq_num describes the PMU overflow interrupt number for the
> >> specified
> >> vcpu_index vcpu. This interrupt could be a PPI or SPI, but for one
> >> VM the
> >> interrupt type must be same for each vcpu.
> >
> > some formatting snafus that I expect come from pasting the text in an
> > e-mail client.
> >
> >>
> >> Errors:
> >> -ENXIO: Getting or setting this attribute is not yet supported
> >
> > 'not yet supported' as in something we'll implement later, or as in you
> > need to call this other function before you can access this state?
> >
> Since only when the group is not KVM_DEV_ARM_PMU_GRP_IRQ, it will return
> -ENXIO. So what about this?
>
> "-ENXIO: Unsupported attribute group"
>
better,

-Christoffer