NAK: [bionic:linux-azure-4.15][PATCH 0/2] LP#:1875467: Enable invariant TSC

[Kelsey Skunberg]

Error in BugLink (s/http/https). Sending a v2.

-Kelsey

On Tue, Jun 9, 2020 at 10:20 PM Kelsey Skunberg
<kelsey.skunberg at canonical.com> wrote:
>
> BugLink: http://bugs.launchpad.net/bugs/1875467
>
> These requested commits will enable support for Invariant TSC
> in Linux guest VMs. The invariant TSC means that the TSC continues at a
> fixed rate regardless of the C-state or frequency of the processor (as
> long as the processor remains in the ACPI S0 state).
>
> These patches will allow guests to access the
> HvSyntheticInvariantTscControl MSR and set bit 0 of this synthetic MSR,
> which then enables the InvariantTSC feature. After setting the synthetic
> MSR, CPUID will enumerate support for InvariantTSC.
>
> The following two commits enable support:
>
> 9e0333ae38ee ("clocksource/drivers/hyper-v: Set TSC clocksource as
> default w/ InvariantTSC") - Changes are the same, though done in
> arch/x86/hyperv/hv_init.c instead of drivers/clocksource/hyperv_timer.
>
> dce7cd62754b ("x86/hyperv: Allow guests to enable InvariantTSC") -
> required context changes to be backported.
>
> Verify
> Andrea Parri (2):
>   x86/hyperv: Allow guests to enable InvariantTSC
>   x86/hyperv: Set TSC clocksource as default w/ InvariantTSC
>
>  arch/x86/hyperv/hv_init.c          | 13 +++++++++++--
>  arch/x86/include/asm/hyperv-tlfs.h |  6 ++++++
>  arch/x86/kernel/cpu/mshyperv.c     |  7 ++++++-
>  3 files changed, 23 insertions(+), 3 deletions(-)
>
> --
> 2.25.1
>