From e12c8f36f3f7a60d55938c5aed5999278fa92bcb Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Tue, 30 Aug 2016 16:14:00 +0800 Subject: KVM: lapic: adjust preemption timer correctly when goes TSC backward MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit TSC_OFFSET will be adjusted if discovers TSC backward during vCPU load. The preemption timer, which relies on the guest tsc to reprogram its preemption timer value, is also reprogrammed if vCPU is scheded in to a different pCPU. However, the current implementation reprogram preemption timer before TSC_OFFSET is adjusted to the right value, resulting in the preemption timer firing prematurely. This patch fix it by adjusting TSC_OFFSET before reprogramming preemption timer if TSC backward. Cc: Paolo Bonzini Cc: Radim Krċmář Cc: Yunhong Jiang Signed-off-by: Wanpeng Li Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 19f9f9e05c2a..699f8726539a 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2743,16 +2743,16 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) if (tsc_delta < 0) mark_tsc_unstable("KVM discovered backwards TSC"); - if (kvm_lapic_hv_timer_in_use(vcpu) && - kvm_x86_ops->set_hv_timer(vcpu, - kvm_get_lapic_tscdeadline_msr(vcpu))) - kvm_lapic_switch_to_sw_timer(vcpu); if (check_tsc_unstable()) { u64 offset = kvm_compute_tsc_offset(vcpu, vcpu->arch.last_guest_tsc); kvm_x86_ops->write_tsc_offset(vcpu, offset); vcpu->arch.tsc_catchup = 1; } + if (kvm_lapic_hv_timer_in_use(vcpu) && + kvm_x86_ops->set_hv_timer(vcpu, + kvm_get_lapic_tscdeadline_msr(vcpu))) + kvm_lapic_switch_to_sw_timer(vcpu); /* * On a host with synchronized TSC, there is no need to update * kvmclock on vcpu->cpu migration -- cgit v1.2.3 From a4497a86fb9b855c5ac8503fdc959393b00bb643 Mon Sep 17 00:00:00 2001 From: Prarit Bhargava Date: Thu, 8 Sep 2016 10:15:28 -0400 Subject: x86, clock: Fix kvm guest tsc initialization MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: Paolo Bonzini Cc: Radim Krčmář Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: x86@kernel.org Cc: Len Brown Cc: "Peter Zijlstra (Intel)" Cc: Borislav Petkov Cc: Adrian Hunter Cc: "Christopher S. Hall" Cc: David Woodhouse Cc: kvm@vger.kernel.org Signed-off-by: Paolo Bonzini --- arch/x86/kernel/kvmclock.c | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86') diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index 1d39bfbd26bb..3692249a70f1 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 -- cgit v1.2.3