Re: [PATCH v2 2/2] KVM: arm64: Document PMU filtering API
From: Auger Eric <eric.auger@redhat.com>
Date: 2020-03-09 18:17:26
Also in:
kvm, kvmarm
Hi Marc, On 3/9/20 1:48 PM, Marc Zyngier wrote:
quoted hunk ↗ jump to hunk
Add a small blurb describing how the event filtering API gets used. Signed-off-by: Marc Zyngier <maz@kernel.org> --- 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 =================================
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