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 aa297292 ("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 aa297292, 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 aa297292. 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: aa297292 ("x86/tsc: Enumerate SKL cpu_khz and tsc_khz via CPUID") Signed-off-by: NPrarit 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: NPaolo Bonzini <pbonzini@redhat.com>
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