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KVM PV clock changes for 6.15:

Browse source 
- Don't take kvm->lock when iterating over vCPUs in the suspend notifier to
    fix a largely theoretical deadlock.
 
  - Use the vCPU's actual Xen PV clock information when starting the Xen timer,
    as the cached state in arch.hv_clock can be stale/bogus.
 
  - Fix a bug where KVM could bleed PVCLOCK_GUEST_STOPPED across different
    PV clocks.
 
  - Restrict PVCLOCK_GUEST_STOPPED to kvmclock, as KVM's suspend notifier only
    accounts for kvmclock, and there's no evidence that the flag is actually
    supported by Xen guests.
 
  - Clean up the per-vCPU "cache" of its reference pvclock, and instead only
    track the vCPU's TSC scaling (multipler+shift) metadata (which is moderately
    expensive to compute, and rarely changes for modern setups).
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Merge tag 'kvm-x86-pvclock-6.15' of https://github.com/kvm-x86/linux into HEAD

KVM PV clock changes for 6.15:

 - Don't take kvm->lock when iterating over vCPUs in the suspend notifier to
   fix a largely theoretical deadlock.

 - Use the vCPU's actual Xen PV clock information when starting the Xen timer,
   as the cached state in arch.hv_clock can be stale/bogus.

 - Fix a bug where KVM could bleed PVCLOCK_GUEST_STOPPED across different
   PV clocks.

 - Restrict PVCLOCK_GUEST_STOPPED to kvmclock, as KVM's suspend notifier only
   accounts for kvmclock, and there's no evidence that the flag is actually
   supported by Xen guests.

 - Clean up the per-vCPU "cache" of its reference pvclock, and instead only
   track the vCPU's TSC scaling (multipler+shift) metadata (which is moderately
   expensive to compute, and rarely changes for modern setups).
This commit is contained in:
Paolo Bonzini 2025-03-19 09:11:59 -04:00
commit fcce7c1e7d
3 changed files with 121 additions and 66 deletions
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