KVM: x86: Drop vm_init_tsc

This is used only by the VMX code, and is not done properly;
if the TSC is indeed backwards, it is out of sync, and will
need proper handling in the logic at each and every CPU change.
For now, drop this test during init as misguided.
Signed-off-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -394,7 +394,6 @@ struct kvm_arch {
 	gpa_t ept_identity_map_addr;
 
 	unsigned long irq_sources_bitmap;
-	u64 vm_init_tsc;
 	s64 kvmclock_offset;
 
 	struct kvm_xen_hvm_config xen_hvm_config;

arch/x86/kvm/vmx.c

@@ -2512,7 +2512,7 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
 {
 	u32 host_sysenter_cs, msr_low, msr_high;
 	u32 junk;
-	u64 host_pat, tsc_this, tsc_base;
+	u64 host_pat, tsc_this;
 	unsigned long a;
 	struct desc_ptr dt;
 	int i;
@@ -2653,12 +2653,8 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
 		vmx->vcpu.arch.cr4_guest_owned_bits |= X86_CR4_PGE;
 	vmcs_writel(CR4_GUEST_HOST_MASK, ~vmx->vcpu.arch.cr4_guest_owned_bits);
 
-	tsc_base = vmx->vcpu.kvm->arch.vm_init_tsc;
-	rdtscll(tsc_this);
-	if (tsc_this < vmx->vcpu.kvm->arch.vm_init_tsc)
-		tsc_base = tsc_this;
-
-	guest_write_tsc(0, tsc_base);
+	tsc_this = native_read_tsc();
+	guest_write_tsc(0, tsc_this);
 
 	return 0;
 }

arch/x86/kvm/x86.c

@@ -5495,8 +5495,6 @@ struct  kvm *kvm_arch_create_vm(void)
 	/* Reserve bit 0 of irq_sources_bitmap for userspace irq source */
 	set_bit(KVM_USERSPACE_IRQ_SOURCE_ID, &kvm->arch.irq_sources_bitmap);
 
-	rdtscll(kvm->arch.vm_init_tsc);
-
 	return kvm;
 }