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KVM: arm64: timers: Allow userspace to set the global counter offset

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And this is the moment you have all been waiting for: setting the
counter offset from userspace.

We expose a brand new capability that reports the ability to set
the offset for both the virtual and physical sides.

In keeping with the architecture, the offset is expressed as
a delta that is substracted from the physical counter value.

Once this new API is used, there is no going back, and the counters
cannot be written to to set the offsets implicitly (the writes
are instead ignored).

Reviewed-by: Colton Lewis <coltonlewis@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230330174800.2677007-8-maz@kernel.org
This commit is contained in:
Marc Zyngier
2023-03-30 18:47:47 +01:00
parent 96906a9150
commit 30ec7997d1
5 changed files with 73 additions and 5 deletions
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3
include/uapi/linux/kvm.h
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@@ -1184,6 +1184,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_S390_PROTECTED_ASYNC_DISABLE 224
#define KVM_CAP_DIRTY_LOG_RING_WITH_BITMAP 225
#define KVM_CAP_PMU_EVENT_MASKED_EVENTS 226
#define KVM_CAP_COUNTER_OFFSET 227
#ifdef KVM_CAP_IRQ_ROUTING
@@ -1543,6 +1544,8 @@ struct kvm_s390_ucas_mapping {
#define KVM_SET_PMU_EVENT_FILTER _IOW(KVMIO, 0xb2, struct kvm_pmu_event_filter)
#define KVM_PPC_SVM_OFF _IO(KVMIO, 0xb3)
#define KVM_ARM_MTE_COPY_TAGS _IOR(KVMIO, 0xb4, struct kvm_arm_copy_mte_tags)
/* Available with KVM_CAP_COUNTER_OFFSET */
#define KVM_ARM_SET_COUNTER_OFFSET _IOW(KVMIO, 0xb5, struct kvm_arm_counter_offset)
/* ioctl for vm fd */
#define KVM_CREATE_DEVICE _IOWR(KVMIO, 0xe0, struct kvm_create_device)