diff options
| author | Marc Zyngier <maz@kernel.org> | 2025-04-09 11:53:15 +0100 |
|---|---|---|
| committer | Marc Zyngier <maz@kernel.org> | 2025-04-11 13:08:23 +0100 |
| commit | b7628c7973765c856866b3047c9002ae0825add6 (patch) | |
| tree | 8da02e190846d06fd47f90cb1d1d068b8af2c41e /Documentation/virt | |
| parent | 022435334393d56f4d6bc398cf16430067807b0a (diff) | |
KVM: arm64: Allow userspace to limit the number of PMU counters for EL2 VMs
As long as we had purely EL1 VMs, we could easily update the number
of guest-visible counters by letting userspace write to PMCR_EL0.N.
With VMs started at EL2, PMCR_EL1.N only reflects MDCR_EL2.HPMN,
and we don't have a good way to limit it.
For this purpose, introduce a new PMUv3 attribute that allows
limiting the maximum number of counters. This requires the explicit
selection of a PMU.
Suggested-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Diffstat (limited to 'Documentation/virt')
| -rw-r--r-- | Documentation/virt/kvm/devices/vcpu.rst | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/devices/vcpu.rst b/Documentation/virt/kvm/devices/vcpu.rst index 31a9576c07af..60bf205cb373 100644 --- a/Documentation/virt/kvm/devices/vcpu.rst +++ b/Documentation/virt/kvm/devices/vcpu.rst @@ -137,6 +137,30 @@ exit_reason = KVM_EXIT_FAIL_ENTRY and populate the fail_entry struct by setting hardare_entry_failure_reason field to KVM_EXIT_FAIL_ENTRY_CPU_UNSUPPORTED and the cpu field to the processor id. +1.5 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS +-------------------------------------------------- + +:Parameters: in kvm_device_attr.addr the address to an unsigned int + representing the maximum value taken by PMCR_EL0.N + +:Returns: + + ======= ==================================================== + -EBUSY PMUv3 already initialized, a VCPU has already run or + an event filter has already been set + -EFAULT Error accessing the value pointed to by addr + -ENODEV PMUv3 not supported or GIC not initialized + -EINVAL No PMUv3 explicitly selected, or value of N out of + range + ======= ==================================================== + +Set the number of implemented event counters in the virtual PMU. This +mandates that a PMU has explicitly been selected via +KVM_ARM_VCPU_PMU_V3_SET_PMU, and will fail when no PMU has been +explicitly selected, or the number of counters is out of range for the +selected PMU. Selecting a new PMU cancels the effect of setting this +attribute. + 2. GROUP: KVM_ARM_VCPU_TIMER_CTRL ================================= |