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4f5758fc67
This commit exports the following information to user-space via the newly created per-vcpu debugfs directory: - TSC offset (as a signed number) - TSC scaling ratio - TSC scaling ratio fractinal bits The original intention of this commit was to export only the TSC offset, but the TSC scaling information is exported for completeness. We need to retrieve the TSC offset from user-space in order to support the merging of host and guest traces in trace-cmd. Today, we use the kvm_write_tsc_offset tracepoint, but it has a number of problems (mainly, it requires a running VM to be rebooted, ftrace setup, and also tracepoints are not supposed to be ABIs). The merging of host and guest traces is explained in more detail in this thread: [Qemu-devel] [RFC] host and guest kernel trace merging https://lists.nongnu.org/archive/html/qemu-devel/2016-03/msg00887.html This commit creates the following files in debugfs: /sys/kernel/debug/kvm/66828-10/vcpu0/tsc-offset /sys/kernel/debug/kvm/66828-10/vcpu0/tsc-scaling-ratio /sys/kernel/debug/kvm/66828-10/vcpu0/tsc-scaling-ratio-frac-bits The last two are only created if TSC scaling is supported. Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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