kvm: RSEQ: Add RSEQ support #12260
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kvm: RSEQ: Add RSEQ support #12260
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This change adds RSEQ support for platform/kvm. To support RSEQ, the KVM platform must provide two key capabilities: (1) A stable, unique CPU ID. (2) A way to detect when a thread as been preempted. This implementation provides the necessary support as follows: CPU ID: - platform/kvm now advertises the KVM vCPU ID as the cpu_id Preemption Detection: - Compares the last context the CPU ran against the current context being scheduled. - Compares the context's rseqCPU and CPU ID retrieved by the platform To facilitate this, several new methods are introduced to the platform interface and implemented by platform/kvm: - HasCpuNumbers() - NumCPUs() - DetectsCPUPreemption() - PreemptCpu() - PreemptAllCpus() A new user-facing KVM specific option, use_cpu_numbers, is introduced to effectively feature guard RSEQ. When use_cpu_numbers is true, vCPU IDs are exposed to the guest, enabling RSEQ support. Setting it to false reverts to the previous behavior and effectively disables RSEQ for applications that rely on it. PiperOrigin-RevId: 823228013
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kvm: RSEQ: Add RSEQ support
This change adds RSEQ support for platform/kvm.
To support RSEQ, the KVM platform must provide two key capabilities:
(1) A stable, unique CPU ID.
(2) A way to detect when a thread as been preempted.
This implementation provides the necessary support as follows:
CPU ID:
Preemption Detection:
scheduled.
To facilitate this, several new methods are introduced to the platform
interface and implemented by platform/kvm:
A new user-facing KVM specific option, use_cpu_numbers, is introduced to
effectively feature guard RSEQ. When use_cpu_numbers is true, vCPU IDs are
exposed to the guest, enabling RSEQ support. Setting it to false reverts to
the previous behavior and effectively disables RSEQ for applications that
rely on it.