[focal:linux-azure/eoan:linux-azure][PATCH 0/2] LP#1875467: Enable invariant TSC support

[Kelsey Skunberg]

Hi Juerg,

On Wed, Jun 10, 2020 at 4:33 AM Juerg Haefliger
<juerg.haefliger at canonical.com> wrote:
>
> On Tue,  9 Jun 2020 23:32:53 -0600
> Kelsey Skunberg <kelsey.skunberg at canonical.com> wrote:
>
> > BugLink: http://bugs.launchpad.net/bugs/1875467
>
> That should be https://...
>
> ...Juerg

oomph, did this on the other set too. Will get this fixed and send a
v2. Thanks for checking!

-Kelsey

>
>
> > Microsoft would like to request two commits in all releases supported on
> > Azure. These commits benefit SAP workloads.
> >
> > 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")
> > dce7cd62754b ("x86/hyperv: Allow guests to enable InvariantTSC")
> >
> > Clean cherry-pick for both commits.
> >
> > Andrea Parri (2):
> >   x86/hyperv: Allow guests to enable InvariantTSC
> >   clocksource/drivers/hyper-v: Set TSC clocksource as default w/
> >     InvariantTSC
> >
> >  arch/x86/include/asm/hyperv-tlfs.h |  5 +++++
> >  arch/x86/kernel/cpu/mshyperv.c     |  7 ++++++-
> >  drivers/clocksource/hyperv_timer.c | 12 ++++++++++--
> >  3 files changed, 21 insertions(+), 3 deletions(-)
> >
>