Hi, We need to retrieve a VM's TSC offset in order to use the host's TSC to merge host and guest traces. This is explained in 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 Today, the only way to retrieve a VM's TSC offset is by using the kvm_write_tsc_offset tracepoint. This has a few problems. First, the tracepoint is only emitted when the VM boots, which requires a reboot to get it if the VM is already running. Second, tracepoints are not supposed to be ABIs in case they need to be consumed by user-space tools. This series exports a VM's TSC offset to user-space via debugfs. A new file called "tsc-offset" is created in the VM's debugfs directory. For example: /sys/kernel/debug/kvm/51696-10/tsc-offset This file contains one TSC offset per line, for each vCPU. For example: vcpu0: 18446742405270834952 vcpu1: 18446742405270834952 vcpu2: 18446742405270834952 vcpu3: 18446742405270834952 Please, see patch 4/4 for additional details. Luiz Capitulino (4): kvm: kvm_destroy_vm_debugfs(): check debugs_stat_data pointer kvm: kvm_create_vm_debugfs(): cleanup on error kvm: add stub for arch specific debugfs support kvm: x86: export TSC offset to user-space arch/arm/kvm/arm.c | 5 +++++ arch/mips/kvm/mips.c | 5 +++++ arch/powerpc/kvm/powerpc.c | 5 +++++ arch/s390/kvm/kvm-s390.c | 5 +++++ arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/svm.c | 1 + arch/x86/kvm/vmx.c | 8 ++++++++ arch/x86/kvm/x86.c | 35 +++++++++++++++++++++++++++++++++++ include/linux/kvm_host.h | 2 ++ virt/kvm/kvm_main.c | 22 ++++++++++++++++------ 10 files changed, 83 insertions(+), 6 deletions(-) -- 2.5.5 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
