Enable Invariant TSC Support

[Joseph Salisbury]

[Impact]

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")

[Test Case]

If the hardware supports TSC scaling, Hyper-V will set bit 15 of the HV_PARTITION_PRIVILEGE_MASK in guest VMs with a compatible Hyper-V configuration version. Bit 15 corresponds to the AccessTscInvariantControls privilege. If this privilege bit is set, guests can access the HvSyntheticInvariantTscControl MSR: guests can set bit 0 of this synthetic MSR to enable the InvariantTSC feature.
After setting the synthetic MSR, CPUID will enumerate support for InvariantTSC.

To check available and current clocksource, run the following:

cat /sys/devices/system/clocksource/clocksource0/available_clocksource
cat /sys/devices/system/clocksource/clocksource0/current_clocksource

[Regression Potential]

If the patches fail to enable support for Invariant TSC or doesn't set the TSC clocksource as the default when Invariant TSC is available, while this would be an error it wouldn't be a regression. Possibility of finding problems using the TSC clocksource once support has been enabled.

a 4.15 test kernel was sent to Microsoft for testing. Result came back verified to allow enabling support for Invariant TSC and there was no report of known regression.

The 4.15, 5.3, & 5.4 kernels with patches applied were boot tested and verified no changes to dmesg logs relating to clocksource or tsc. tsc autotest ran successfully on the 4.15 before and after applying the requested patches.

We are no longer interested in applying to Eoan/linux-azure (5.3) and
only targeted to apply the patches to bionic/azure-4.15 and focal/azure.

[Po-Hsu Lin (cypressyew)]

Hi Joe,

I have Eoan and Focal test kernel built with these 2 patches, can you give them a try?
https://people.canonical.com/~phlin/kernel/lp-1875467-azure-tsc/

I am not sure if it worth it to patch this in older kernels. Before Eoan the drivers/clocksource/hyperv_timer.c haven't been split out from drivers/hv/hv.c yet.

[Po-Hsu Lin (cypressyew)]

Oh looks like this is in progress by Kelsey:
https://lists.ubuntu.com/archives/kernel-team/2020-June/110949.html
https://lists.ubuntu.com/archives/kernel-team/2020-June/110952.html

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-azure-4.15 - 4.15.0-1096.106

---------------
linux-azure-4.15 (4.15.0-1096.106) bionic; urgency=medium

  * bionic/linux-azure-4.15: 4.15.0-1096.106 -proposed tracker (LP: #1894683)

  * Mellanox Check For Write Combining Support (LP: #1874503)
    - RDMA/rxe: Close a race after ib_register_device
    - IB/mlx5: Align usage of QP1 create flags with rest of mlx5 defines
    - IB/mlx5: Test write combining support

  * Enable Invariant TSC Support (LP: #1875467)
    - x86/hyperv: Allow guests to enable InvariantTSC
    - x86/hyperv: Set TSC clocksource as default w/ InvariantTSC

  * Only notify Hyper-V for die events that are oops (LP: #1891222)
    - Drivers: hv: vmbus: Only notify Hyper-V for die events that are oops

  * speed for CX4 VF showing as unknown in ethtool output (LP: #1876770)
    - net/mlx5: Expose link speed directly
    - net/mlx5: Expose port speed when possible
    - net/mlx5: Tidy up and fix reverse christmas ordring

  [ Ubuntu: 4.15.0-118.119 ]

  * bionic/linux: 4.15.0-118.119 -proposed tracker (LP: #1894697)
  * Packaging resync (LP: #1786013)
    - update dkms package versions
  * Introduce the new NVIDIA 450-server and the 450 UDA series (LP: #1887674)
    - [packaging] add signed modules for nvidia 450 and 450-server
  * cgroup refcount is bogus when cgroup_sk_alloc is disabled (LP: #1886860)
    - cgroup: add missing skcd->no_refcnt check in cgroup_sk_clone()
  * CVE-2020-12888
    - vfio/type1: Support faulting PFNMAP vmas
    - vfio-pci: Fault mmaps to enable vma tracking
    - vfio-pci: Invalidate mmaps and block MMIO access on disabled memory
  * [Hyper-V] VSS and File Copy daemons intermittently fails to start
    (LP: #1891224)
    - [Packaging] Bind hv_vss_daemon startup to hv_vss device
    - [Packaging] bind hv_fcopy_daemon startup to hv_fcopy device
  * KVM: Fix zero_page reference counter overflow when using KSM on KVM compute
    host (LP: #1837810)
    - KVM: fix overflow of zero page refcount with ksm running
  * Fix false-negative return value for rtnetlink.sh in kselftests/net
    (LP: #1890136)
    - selftests: rtnetlink: correct the final return value for the test
    - selftests: rtnetlink: make kci_test_encap() return sub-test result
  * Bionic update: upstream stable patchset 2020-08-18 (LP: #1892091)
    - USB: serial: qcserial: add EM7305 QDL product ID
    - USB: iowarrior: fix up report size handling for some devices
    - usb: xhci: define IDs for various ASMedia host controllers
    - usb: xhci: Fix ASMedia ASM1142 DMA addressing
    - Revert "ALSA: hda: call runtime_allow() for all hda controllers"
    - ALSA: seq: oss: Serialize ioctls
    - staging: android: ashmem: Fix lockdep warning for write operation
    - Bluetooth: Fix slab-out-of-bounds read in hci_extended_inquiry_result_evt()
    - Bluetooth: Prevent out-of-bounds read in hci_inquiry_result_evt()
    - Bluetooth: Prevent out-of-bounds read in hci_inquiry_result_with_rssi_evt()
    - omapfb: dss: Fix max fclk divider for omap36xx
    - binder: Prevent context manager from incrementing ref 0
    - vgacon: Fix for missing check in scrollback handling
    - mtd: properly check all write i...

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-azure - 4.15.0-1096.106~16.04.1

---------------
linux-azure (4.15.0-1096.106~16.04.1) xenial; urgency=medium

  * xenial/linux-azure: 4.15.0-1096.106~16.04.1 -proposed tracker (LP: #1894681)

  [ Ubuntu: 4.15.0-1096.106 ]

  * bionic/linux-azure-4.15: 4.15.0-1096.106 -proposed tracker (LP: #1894683)
  * Mellanox Check For Write Combining Support (LP: #1874503)
    - RDMA/rxe: Close a race after ib_register_device
    - IB/mlx5: Align usage of QP1 create flags with rest of mlx5 defines
    - IB/mlx5: Test write combining support
  * Enable Invariant TSC Support (LP: #1875467)
    - x86/hyperv: Allow guests to enable InvariantTSC
    - x86/hyperv: Set TSC clocksource as default w/ InvariantTSC
  * Only notify Hyper-V for die events that are oops (LP: #1891222)
    - Drivers: hv: vmbus: Only notify Hyper-V for die events that are oops
  * speed for CX4 VF showing as unknown in ethtool output (LP: #1876770)
    - net/mlx5: Expose link speed directly
    - net/mlx5: Expose port speed when possible
    - net/mlx5: Tidy up and fix reverse christmas ordring
  * bionic/linux: 4.15.0-118.119 -proposed tracker (LP: #1894697)
  * Packaging resync (LP: #1786013)
    - update dkms package versions
  * Introduce the new NVIDIA 450-server and the 450 UDA series (LP: #1887674)
    - [packaging] add signed modules for nvidia 450 and 450-server
  * cgroup refcount is bogus when cgroup_sk_alloc is disabled (LP: #1886860)
    - cgroup: add missing skcd->no_refcnt check in cgroup_sk_clone()
  * CVE-2020-12888
    - vfio/type1: Support faulting PFNMAP vmas
    - vfio-pci: Fault mmaps to enable vma tracking
    - vfio-pci: Invalidate mmaps and block MMIO access on disabled memory
  * [Hyper-V] VSS and File Copy daemons intermittently fails to start
    (LP: #1891224)
    - [Packaging] Bind hv_vss_daemon startup to hv_vss device
    - [Packaging] bind hv_fcopy_daemon startup to hv_fcopy device
  * KVM: Fix zero_page reference counter overflow when using KSM on KVM compute
    host (LP: #1837810)
    - KVM: fix overflow of zero page refcount with ksm running
  * Fix false-negative return value for rtnetlink.sh in kselftests/net
    (LP: #1890136)
    - selftests: rtnetlink: correct the final return value for the test
    - selftests: rtnetlink: make kci_test_encap() return sub-test result
  * Bionic update: upstream stable patchset 2020-08-18 (LP: #1892091)
    - USB: serial: qcserial: add EM7305 QDL product ID
    - USB: iowarrior: fix up report size handling for some devices
    - usb: xhci: define IDs for various ASMedia host controllers
    - usb: xhci: Fix ASMedia ASM1142 DMA addressing
    - Revert "ALSA: hda: call runtime_allow() for all hda controllers"
    - ALSA: seq: oss: Serialize ioctls
    - staging: android: ashmem: Fix lockdep warning for write operation
    - Bluetooth: Fix slab-out-of-bounds read in hci_extended_inquiry_result_evt()
    - Bluetooth: Prevent out-of-bounds read in hci_inquiry_result_evt()
    - Bluetooth: Prevent out-of-bounds read in hci_inquiry_result_with_rssi_evt()
    - omapfb: dss: Fix max fclk divider for omap36xx
    - binder: Prevent context manager from incrementing ref 0
    - vgacon...

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-azure - 5.4.0-1026.26

---------------
linux-azure (5.4.0-1026.26) focal; urgency=medium

  * focal/linux-azure: 5.4.0-1026.26 -proposed tracker (LP: #1894641)

  * Mellanox Check For Write Combining Support (LP: #1874503)
    - IB/mlx5: Align usage of QP1 create flags with rest of mlx5 defines
    - IB/mlx5: Test write combining support

  * Enable Invariant TSC Support (LP: #1875467)
    - x86/hyperv: Allow guests to enable InvariantTSC
    - clocksource/drivers/hyper-v: Set TSC clocksource as default w/ InvariantTSC

  * Only notify Hyper-V for die events that are oops (LP: #1891222)
    - Drivers: hv: vmbus: Only notify Hyper-V for die events that are oops

  * speed for CX4 VF showing as unknown in ethtool output (LP: #1876770)
    - net/mlx5: Expose link speed directly
    - net/mlx5: Expose port speed when possible
    - net/mlx5: Tidy up and fix reverse christmas ordring

  [ Ubuntu: 5.4.0-48.52 ]

  * focal/linux: 5.4.0-48.52 -proposed tracker (LP: #1894654)
  * mm/slub kernel oops on focal kernel 5.4.0-45 (LP: #1895109)
    - SAUCE: Revert "mm/slub: fix a memory leak in sysfs_slab_add()"
  * Packaging resync (LP: #1786013)
    - update dkms package versions
    - update dkms package versions
  * Introduce the new NVIDIA 450-server and the 450 UDA series (LP: #1887674)
    - [packaging] add signed modules for nvidia 450 and 450-server
  * [UBUNTU 20.04] zPCI attach/detach issues with PF/VF linking support
    (LP: #1892849)
    - s390/pci: fix zpci_bus_link_virtfn()
    - s390/pci: re-introduce zpci_remove_device()
    - s390/pci: fix PF/VF linking on hot plug
  * [UBUNTU 20.04] kernel: s390/cpum_cf,perf: changeDFLT_CCERROR counter name
    (LP: #1891454)
    - s390/cpum_cf, perf: change DFLT_CCERROR counter name
  * [UBUNTU 20.04] zPCI: Enabling of a reserved PCI function regression
    introduced by multi-function support (LP: #1891437)
    - s390/pci: fix enabling a reserved PCI function
  * CVE-2020-12888
    - vfio/type1: Support faulting PFNMAP vmas
    - vfio-pci: Fault mmaps to enable vma tracking
    - vfio-pci: Invalidate mmaps and block MMIO access on disabled memory
  * [Hyper-V] VSS and File Copy daemons intermittently fails to start
    (LP: #1891224)
    - [Packaging] Bind hv_vss_daemon startup to hv_vss device
    - [Packaging] bind hv_fcopy_daemon startup to hv_fcopy device
  * alsa/hdmi: support nvidia mst hdmi/dp audio (LP: #1867704)
    - ALSA: hda - Rename snd_hda_pin_sense to snd_hda_jack_pin_sense
    - ALSA: hda - Add DP-MST jack support
    - ALSA: hda - Add DP-MST support for non-acomp codecs
    - ALSA: hda - Add DP-MST support for NVIDIA codecs
    - ALSA: hda: hdmi - fix regression in connect list handling
    - ALSA: hda: hdmi - fix kernel oops caused by invalid PCM idx
    - ALSA: hda: hdmi - preserve non-MST PCM routing for Intel platforms
    - ALSA: hda: hdmi - Keep old slot assignment behavior for Intel platforms
    - ALSA: hda - Fix DP-MST support for NVIDIA codecs
  * Focal update: v5.4.60 upstream stable release (LP: #1892899)
    - smb3: warn on confusing error scenario with sec=krb5
    - genirq/affinity: Make affinity setting if activated opt-in
    - ...