kernel-packages team mailing list archive

[Joseph Salisbury <joseph.salisbury@xxxxxxxxxxxxx>]

Would it be possible for you to test the latest upstream kernel? Refer
to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest
v4.6 kernel[0].

If this bug is fixed in the mainline kernel, please add the following
tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag:
'kernel-bug-exists-upstream'.

Once testing of the upstream kernel is complete, please mark this bug as
"Confirmed".


Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.6-rc4-wily/


** Changed in: linux (Ubuntu)
   Importance: Undecided => Medium

** Changed in: linux (Ubuntu)
       Status: Confirmed => Incomplete

** Tags added: kernel-da-key

-- 
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1567159

Title:
  Ubuntu 15.10: After hot plug vcpu, kvm_arch->use_master_clock will
  never be true.

Status in linux package in Ubuntu:
  Incomplete

Bug description:
  1. In function kvm_write_tsc, when tsc first matched, do
  kvm->arch.nr_vcpus_matched_tsc++;

  2. In function pvclock_update_vm_gtod_copy, if vcpus_matched (also
  with other conditions meet), ka->use_master_clock will be true;

  3. After hot plug vcpu, kvm_arch_vcpu_postcreate and Qemu will call
  kvm_write_tsc for the new vcpu. Because the tsc will not match, so do
  kvm->arch.nr_vcpus_matched_tsc = 0;

  4. For other already existed vcpu will not call kvm_write_tsc, so will
  not do kvm->arch.nr_vcpus_matched_tsc++;

  5. So vcpus_matched in function pvclock_update_vm_gtod_copy will be
  false forever, this cause ka->use_master_clock will never be true;

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