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

[Thadeu Lima de Souza Cascardo]

On Tue, Jun 09, 2020 at 11:32:53PM -0600, Kelsey Skunberg wrote:
> BugLink: http://bugs.launchpad.net/bugs/1875467
> 
> 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(-)
> 
> -- 
> 2.25.1
> 

As with the bionic patchset, what test has been done here? Thanks.
Cascardo.