I'm queueing patches 2 and 3 for now, since the sane MSR interface is a
prerequisite anyway.
Paolo
On 03/12/20 18:11, Maxim Levitsky wrote:
Hi!
This is the second version of the work to make TSC migration more accurate,
as was defined by Paulo at:
https://www.spinics.net/lists/kvm/msg225525.html
I omitted most of the semi-offtopic points I raised related to TSC
in the previous RFC where we can continue the discussion.
I do want to raise another thing that I almost forgot.
On AMD systems, the Linux kernel will mark the guest tsc as
unstable unless invtsc is set which is set on recent AMD
hardware.
Take a look at 'unsynchronized_tsc()' to verify this.
This is another thing that IMHO should be fixed at least when
running under KVM.
Note that I forgot to mention that
X86_FEATURE_TSC_RELIABLE also short-circuits this code,
thus giving another reason to enable it under KVM.
Changes from V1:
- added KVM_TSC_STATE_TIMESTAMP_VALID instead of testing ns == 0
- allow diff < 0, because it is still better that capping it to 0
- updated tsc_msr_test unit test to cover this feature
- refactoring
Patches to enable this feature in qemu are in the process of
being sent to qemu-devel mailing list.
Best regards,
Maxim Levitsky
Maxim Levitsky (3):
KVM: x86: implement KVM_{GET|SET}_TSC_STATE
KVM: x86: introduce KVM_X86_QUIRK_TSC_HOST_ACCESS
kvm/selftests: update tsc_msrs_test to cover
KVM_X86_QUIRK_TSC_HOST_ACCESS
Documentation/virt/kvm/api.rst | 65 +++++++++++++
arch/x86/include/uapi/asm/kvm.h | 1 +
arch/x86/kvm/x86.c | 92 ++++++++++++++++++-
include/uapi/linux/kvm.h | 15 +++
.../selftests/kvm/x86_64/tsc_msrs_test.c | 79 ++++++++++++++--
5 files changed, 237 insertions(+), 15 deletions(-)
