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author | Peng Hao <peng.hao2@zte.com.cn> | 2018-07-14 23:28:29 +0800 |
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committer | Paolo Bonzini <pbonzini@redhat.com> | 2018-07-18 11:43:17 +0200 |
commit | e10f7805032365cc11c739a97f226ebb48aee042 (patch) | |
tree | fe7cf33daa3ef5a8fc7ae2a1ae64a417686c9860 /arch | |
parent | 2307af1c4b2e0ad886f30e31739845322cbd328b (diff) | |
download | linux-e10f7805032365cc11c739a97f226ebb48aee042.tar.bz2 |
kvmclock: fix TSC calibration for nested guests
Inside a nested guest, access to hardware can be slow enough that
tsc_read_refs always return ULLONG_MAX, causing tsc_refine_calibration_work
to be called periodically and the nested guest to spend a lot of time
reading the ACPI timer.
However, if the TSC frequency is available from the pvclock page,
we can just set X86_FEATURE_TSC_KNOWN_FREQ and avoid the recalibration.
'refine' operation.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
[Commit message rewritten. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r-- | arch/x86/kernel/kvmclock.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index d79a18b4cf9d..4c53d12ca933 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -138,6 +138,7 @@ static unsigned long kvm_get_tsc_khz(void) src = &hv_clock[cpu].pvti; tsc_khz = pvclock_tsc_khz(src); put_cpu(); + setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); return tsc_khz; } |