APPLIED: [SRU][S:linux-azure/R:linux-azure/N:linux-azure/J:linux-azure][PATCH 0/2] Revert SAUCE: AMDv4 VMs may get no timer interrupts or suffer from timer interrupt storms

[John Cabaj]

On 9/22/26 3:53 PM, John Cabaj wrote:
> BugLink: https://bugs.launchpad.net/bugs/2167893
> 
> SRU Justification
> 
> [Impact]
> 
> * Microsoft requested patches to work around intermittent deployment failures on AMDv4 VM sizes due to issues with large values of Hyper-V timer as part of LP: #2137674. Fixes in the hypervisor have been rolled out, so the SAUCE patches can be reverted.
> 
> [Fix]
> Revert the following SAUCE patches
>    - "UBUNTU: SAUCE: clocksource: hyper-v: do not use an insanely big TSC in hv_read_tsc_page_tsc()"
>    - "UBUNTU: SAUCE: clocksource: hyper-v: use the APIC timer if the Hyper-V timer is unreliable on some CPUs"
> 
> [Test Plan]
> 
> * Compile tested
> * Microsoft tested
> 
> [Regression potential]
> 
> * Upstream changes are largely localized to time and clock source functions, and have been upstream for some time. Regression likliehood is slim.
> * Possible regressions could result in unexpected behavior of Hyper-V driver.
> 
> [Other info]
> 
> * SF#00422328
> 
> John Cabaj (2):
>    Revert "UBUNTU: SAUCE: clocksource: hyper-v: use the APIC timer if the
>      Hyper-V timer is unreliable on some CPUs"
>    Revert "UBUNTU: SAUCE: clocksource: hyper-v: do not use an insanely
>      big TSC in hv_read_tsc_page_tsc()"
> 
>   arch/x86/kernel/cpu/mshyperv.c     | 43 ------------------------------
>   drivers/clocksource/hyperv_timer.c |  4 +--
>   include/clocksource/hyperv_timer.h |  4 ---
>   3 files changed, 1 insertion(+), 50 deletions(-)
> 

Applied to Stonking, Resolute, Noble, and Jammy linux-azure master-next 
branches.


Thanks,
j-c