Hi Marc,
On 3/9/20 1:48 PM, Marc Zyngier wrote:
> Add a small blurb describing how the event filtering API gets used.
>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> ---
> Documentation/virt/kvm/devices/vcpu.rst | 40 +++++++++++++++++++++++++
> 1 file changed, 40 insertions(+)
>
> diff --git a/Documentation/virt/kvm/devices/vcpu.rst b/Documentation/virt/kvm/devices/vcpu.rst
> index 9963e680770a..7262c0469856 100644
> --- a/Documentation/virt/kvm/devices/vcpu.rst
> +++ b/Documentation/virt/kvm/devices/vcpu.rst
> @@ -55,6 +55,46 @@ Request the initialization of the PMUv3. If using the PMUv3 with an in-kernel
> virtual GIC implementation, this must be done after initializing the in-kernel
> irqchip.
>
> +1.3 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_FILTER
> +---------------------------------------
> +
> +:Parameters: in kvm_device_attr.addr the address for a PMU event filter is a
> + pointer to a struct kvm_pmu_event_filter
> +
> +:Returns:
> +
> + ======= ======================================================
> + -ENODEV: PMUv3 not supported or GIC not initialized
> + -ENXIO: PMUv3 not properly configured or in-kernel irqchip not
> + configured as required prior to calling this attribute
> + -EBUSY: PMUv3 already initialized
maybe document -EINVAL?
> + ======= ======================================================
> +
> +Request the installation of a PMU event filter describe as follows:
s/describe/described
> +
> +struct kvm_pmu_event_filter {
> + __u16 base_event;
> + __u16 nevents;
> +
> +#define KVM_PMU_EVENT_ALLOW 0
> +#define KVM_PMU_EVENT_DENY 1
> +
> + __u8 action;
> + __u8 pad[3];
> +};
> +
> +A filter range is defined as the range [@base_event, @base_event + @nevents[,
> +together with an @action (KVM_PMU_EVENT_ALLOW or KVM_PMU_EVENT_DENY). The
> +first registered range defines the global policy (global ALLOW if the first
> +@action is DENY, global DENY if the first @action is ALLOW). Multiple ranges
> +can be programmed, and must fit within the 16bit space defined by the ARMv8.1
> +PMU architecture.
what about before 8.1 where the range was 10 bits? Should it be tested
in the code?
nitpicking: It is not totally obvious what does happen if the user space
sets a deny filter on a range and then an allow filter on the same
range. it is supported but may be worth telling so? Also explain the the
default filtering remains "allow" by default?
> +
> +Restrictions: Event 0 (SW_INCR) is never filtered, as it doesn't count a
> +hardware event. Filtering event 0x1E (CHAIN) has no effect either, as it
> +isn't strictly speaking an event. Filtering the cycle counter is possible
> +using event 0x11 (CPU_CYCLES).
Thanks
Eric
> +
>
> 2. GROUP: KVM_ARM_VCPU_TIMER_CTRL
> =================================
>
