From 39497d7660d9866a47a2dc9055672358da57ad3d Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 17 Apr 2019 10:15:32 -0700 Subject: KVM: lapic: Track lapic timer advance per vCPU Automatically adjusting the globally-shared timer advancement could corrupt the timer, e.g. if multiple vCPUs are concurrently adjusting the advancement value. That could be partially fixed by using a local variable for the arithmetic, but it would still be susceptible to a race when setting timer_advance_adjust_done. And because virtual_tsc_khz and tsc_scaling_ratio are per-vCPU, the correct calibration for a given vCPU may not apply to all vCPUs. Furthermore, lapic_timer_advance_ns is marked __read_mostly, which is effectively violated when finding a stable advancement takes an extended amount of timer. Opportunistically change the definition of lapic_timer_advance_ns to a u32 so that it matches the style of struct kvm_timer. Explicitly pass the param to kvm_create_lapic() so that it doesn't have to be exposed to lapic.c, thus reducing the probability of unintentionally using the global value instead of the per-vCPU value. Cc: Liran Alon Cc: Wanpeng Li Reviewed-by: Liran Alon Cc: stable@vger.kernel.org Fixes: 3b8a5df6c4dc6 ("KVM: LAPIC: Tune lapic_timer_advance_ns automatically") Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/vmx.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'arch/x86/kvm/vmx/vmx.c') diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index b4e7d645275a..bcdd69d90a8c 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -7032,6 +7032,7 @@ static int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc) { struct vcpu_vmx *vmx; u64 tscl, guest_tscl, delta_tsc, lapic_timer_advance_cycles; + struct kvm_timer *ktimer = &vcpu->arch.apic->lapic_timer; if (kvm_mwait_in_guest(vcpu->kvm)) return -EOPNOTSUPP; @@ -7040,7 +7041,8 @@ static int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc) tscl = rdtsc(); guest_tscl = kvm_read_l1_tsc(vcpu, tscl); delta_tsc = max(guest_deadline_tsc, guest_tscl) - guest_tscl; - lapic_timer_advance_cycles = nsec_to_cycles(vcpu, lapic_timer_advance_ns); + lapic_timer_advance_cycles = nsec_to_cycles(vcpu, + ktimer->timer_advance_ns); if (delta_tsc > lapic_timer_advance_cycles) delta_tsc -= lapic_timer_advance_cycles; -- cgit v1.2.3