Re: [PATCH v2 0/6] kvm: x86: export TSC information to user-space

From: Paolo Bonzini
Date: Fri Sep 16 2016 - 10:56:50 EST




On 16/09/2016 16:27, Luiz Capitulino wrote:
> [Introduction will follow]
>
> Changelog
> ---------
>
> v2
>
> - add tsc_offset field to struct kvm_vcpu_arch
> - drop read_tsc_offset()
> - add per-vcpu dir entries in debugfs
> - export TSC scaling info (besides TSC offset)
> - export the TSC offset as a signed number
> - drop patch that wrongly tried to improve error
> handling in kvm_create_vm_debugfs()

I've tested this patch on an AMD machine with TSC scaling, so I'm
pushing it shortly to kvm/queue.

Paolo

> Intro
> -----
>
> This series exports a VM's TSC offset and TSC scaling
> information to user-space via a new per-vcpu directory
> in debugfs. For example:
>
> /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 TSC offset in particular is needed in user-space
> in order for tracing tools, such as trace-cmd, to be
> able to merge the host and guest traces using the
> host TSC. 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
>
> Luiz Capitulino (6):
> kvm: x86: add tsc_offset field to struct kvm_vcpu_arch
> kvm: x86: drop read_tsc_offset()
> kvm: kvm_destroy_vm_debugfs(): check debugfs_stat_data pointer
> kvm: add stubs for arch specific debugfs support
> kvm: create per-vcpu dirs in debugfs
> kvm: x86: export TSC information to user-space
>
> arch/arm/kvm/arm.c | 10 ++++++
> arch/mips/kvm/mips.c | 10 ++++++
> arch/powerpc/kvm/powerpc.c | 10 ++++++
> arch/s390/kvm/kvm-s390.c | 10 ++++++
> arch/x86/include/asm/kvm_host.h | 2 +-
> arch/x86/kvm/Makefile | 2 +-
> arch/x86/kvm/debugfs.c | 69 +++++++++++++++++++++++++++++++++++++++++
> arch/x86/kvm/svm.c | 8 -----
> arch/x86/kvm/vmx.c | 6 ----
> arch/x86/kvm/x86.c | 12 +++++--
> include/linux/kvm_host.h | 4 +++
> virt/kvm/kvm_main.c | 40 ++++++++++++++++++++++--
> 12 files changed, 161 insertions(+), 22 deletions(-)
> create mode 100644 arch/x86/kvm/debugfs.c
>