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| author | Marcelo Tosatti <mtosatti@redhat.com> | 2012-11-27 23:29:03 -0200 |
|---|---|---|
| committer | Marcelo Tosatti <mtosatti@redhat.com> | 2012-11-27 23:29:15 -0200 |
| commit | b48aa97e38206a84bf8485e7c553412274708ce5 (patch) | |
| tree | 360f44bce8cf39836e916f3b5ed5c2e8849cd263 /arch/x86/include | |
| parent | 42897d866b120547777ae1fd316680ec53356d9c (diff) | |
| download | linux-b48aa97e38206a84bf8485e7c553412274708ce5.tar.gz | |
KVM: x86: require matched TSC offsets for master clock
With master clock, a pvclock clock read calculates:
ret = system_timestamp + [ (rdtsc + tsc_offset) - tsc_timestamp ]
Where 'rdtsc' is the host TSC.
system_timestamp and tsc_timestamp are unique, one tuple
per VM: the "master clock".
Given a host with synchronized TSCs, its obvious that
guest TSC must be matched for the above to guarantee monotonicity.
Allow master clock usage only if guest TSCs are synchronized.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'arch/x86/include')
| -rw-r--r-- | arch/x86/include/asm/kvm_host.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 32f0e4a063b7..9fb6d8da7a43 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -561,6 +561,7 @@ struct kvm_arch { u64 cur_tsc_write; u64 cur_tsc_offset; u8 cur_tsc_generation; + int nr_vcpus_matched_tsc; spinlock_t pvclock_gtod_sync_lock; bool use_master_clock; |