Allow the caller to pass host tsc value to kvm_x86_ops->read_l1_tsc().

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: vsyscall/arch/x86/include/asm/kvm_host.h
===================================================================
--- vsyscall.orig/arch/x86/include/asm/kvm_host.h
+++ vsyscall/arch/x86/include/asm/kvm_host.h
@@ -703,7 +703,7 @@ struct kvm_x86_ops {
 	void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);
 
 	u64 (*compute_tsc_offset)(struct kvm_vcpu *vcpu, u64 target_tsc);
-	u64 (*read_l1_tsc)(struct kvm_vcpu *vcpu);
+	u64 (*read_l1_tsc)(struct kvm_vcpu *vcpu, u64 host_tsc);
 
 	void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2);
 
Index: vsyscall/arch/x86/kvm/lapic.c
===================================================================
--- vsyscall.orig/arch/x86/kvm/lapic.c
+++ vsyscall/arch/x86/kvm/lapic.c
@@ -1011,7 +1011,7 @@ static void start_apic_timer(struct kvm_
 		local_irq_save(flags);
 
 		now = apic->lapic_timer.timer.base->get_time();
-		guest_tsc = kvm_x86_ops->read_l1_tsc(vcpu);
+		guest_tsc = kvm_x86_ops->read_l1_tsc(vcpu, native_read_tsc());
 		if (likely(tscdeadline > guest_tsc)) {
 			ns = (tscdeadline - guest_tsc) * 1000000ULL;
 			do_div(ns, this_tsc_khz);
Index: vsyscall/arch/x86/kvm/svm.c
===================================================================
--- vsyscall.orig/arch/x86/kvm/svm.c
+++ vsyscall/arch/x86/kvm/svm.c
@@ -3008,11 +3008,11 @@ static int cr8_write_interception(struct
 	return 0;
 }
 
-u64 svm_read_l1_tsc(struct kvm_vcpu *vcpu)
+u64 svm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)
 {
 	struct vmcb *vmcb = get_host_vmcb(to_svm(vcpu));
 	return vmcb->control.tsc_offset +
-		svm_scale_tsc(vcpu, native_read_tsc());
+		svm_scale_tsc(vcpu, host_tsc);
 }
 
 static int svm_get_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 *data)
Index: vsyscall/arch/x86/kvm/vmx.c
===================================================================
--- vsyscall.orig/arch/x86/kvm/vmx.c
+++ vsyscall/arch/x86/kvm/vmx.c
@@ -1839,11 +1839,10 @@ static u64 guest_read_tsc(void)
  * Like guest_read_tsc, but always returns L1's notion of the timestamp
  * counter, even if a nested guest (L2) is currently running.
  */
-u64 vmx_read_l1_tsc(struct kvm_vcpu *vcpu)
+u64 vmx_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)
 {
-	u64 host_tsc, tsc_offset;
+	u64 tsc_offset;
 
-	rdtscll(host_tsc);
 	tsc_offset = is_guest_mode(vcpu) ?
 		to_vmx(vcpu)->nested.vmcs01_tsc_offset :
 		vmcs_read64(TSC_OFFSET);
Index: vsyscall/arch/x86/kvm/x86.c
===================================================================
--- vsyscall.orig/arch/x86/kvm/x86.c
+++ vsyscall/arch/x86/kvm/x86.c
@@ -1175,7 +1175,7 @@ static int kvm_guest_time_update(struct 
 
 	/* Keep irq disabled to prevent changes to the clock */
 	local_irq_save(flags);
-	tsc_timestamp = kvm_x86_ops->read_l1_tsc(v);
+	tsc_timestamp = kvm_x86_ops->read_l1_tsc(v, native_read_tsc());
 	kernel_ns = get_kernel_ns();
 	this_tsc_khz = __get_cpu_var(cpu_tsc_khz);
 	if (unlikely(this_tsc_khz == 0)) {
@@ -5429,7 +5429,8 @@ static int vcpu_enter_guest(struct kvm_v
 	if (hw_breakpoint_active())
 		hw_breakpoint_restore();
 
-	vcpu->arch.last_guest_tsc = kvm_x86_ops->read_l1_tsc(vcpu);
+	vcpu->arch.last_guest_tsc = kvm_x86_ops->read_l1_tsc(vcpu,
+							   native_read_tsc());
 
 	vcpu->mode = OUTSIDE_GUEST_MODE;
 	smp_wmb();