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| author | Prarit Bhargava <prarit@redhat.com> | 2016-09-08 10:15:28 -0400 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-09-08 16:41:55 +0200 |
| commit | a4497a86fb9b855c5ac8503fdc959393b00bb643 (patch) | |
| tree | 7c57080e76a13e5a2afe56f5a6a2195635b17ffb | |
| parent | 20218b86ad8adb4bf71db9425bb59680f345eafd (diff) | |
| download | linux-a4497a86fb9b855c5ac8503fdc959393b00bb643.tar.gz | |
x86, clock: Fix kvm guest tsc initialization
When booting a kvm guest on AMD with the latest kernel the following
messages are displayed in the boot log:
tsc: Unable to calibrate against PIT
tsc: HPET/PMTIMER calibration failed
aa297292d708 ("x86/tsc: Enumerate SKL cpu_khz and tsc_khz via CPUID")
introduced a change to account for a difference in cpu and tsc frequencies for
Intel SKL processors. Before this change the native tsc set
x86_platform.calibrate_tsc to native_calibrate_tsc() which is a hardware
calibration of the tsc, and in tsc_init() executed
tsc_khz = x86_platform.calibrate_tsc();
cpu_khz = tsc_khz;
The kvm code changed x86_platform.calibrate_tsc to kvm_get_tsc_khz() and
executed the same tsc_init() function. This meant that KVM guests did not
execute the native hardware calibration function.
After aa297292d708, there are separate native calibrations for cpu_khz and
tsc_khz. The code sets x86_platform.calibrate_tsc to native_calibrate_tsc()
which is now an Intel specific calibration function, and
x86_platform.calibrate_cpu to native_calibrate_cpu() which is the "old"
native_calibrate_tsc() function (ie, the native hardware calibration
function).
tsc_init() now does
cpu_khz = x86_platform.calibrate_cpu();
tsc_khz = x86_platform.calibrate_tsc();
if (tsc_khz == 0)
tsc_khz = cpu_khz;
else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
cpu_khz = tsc_khz;
The kvm code should not call the hardware initialization in
native_calibrate_cpu(), as it isn't applicable for kvm and it didn't do that
prior to aa297292d708.
This patch resolves this issue by setting x86_platform.calibrate_cpu to
kvm_get_tsc_khz().
v2: I had originally set x86_platform.calibrate_cpu to
cpu_khz_from_cpuid(), however, pbonzini pointed out that the CPUID leaf
in that function is not available in KVM. I have changed the function
pointer to kvm_get_tsc_khz().
Fixes: aa297292d708 ("x86/tsc: Enumerate SKL cpu_khz and tsc_khz via CPUID")
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Len Brown <len.brown@intel.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: "Christopher S. Hall" <christopher.s.hall@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: kvm@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -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 1d39bfbd26bb3..3692249a70f1e 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -289,6 +289,7 @@ void __init kvmclock_init(void) put_cpu(); x86_platform.calibrate_tsc = kvm_get_tsc_khz; + x86_platform.calibrate_cpu = kvm_get_tsc_khz; x86_platform.get_wallclock = kvm_get_wallclock; x86_platform.set_wallclock = kvm_set_wallclock; #ifdef CONFIG_X86_LOCAL_APIC |