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| author | Peng Hao <peng.hao2@zte.com.cn> | 2018-07-14 23:28:29 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-08-24 13:09:18 +0200 |
| commit | 114a5608cde4197870d4f217c69f27ea20f9350c (patch) | |
| tree | b0dea0b7d50ccbafb1175111e82cabc5456df3ff | |
| parent | 1b1968d8f6ae913f5c0ec55893d324195d234fbe (diff) | |
| download | linux-114a5608cde4197870d4f217c69f27ea20f9350c.tar.gz | |
kvmclock: fix TSC calibration for nested guests
[ Upstream commit e10f7805032365cc11c739a97f226ebb48aee042 ]
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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -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 5b609e28ce3f4..48703d430a2fb 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -143,6 +143,7 @@ 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; } |