KVM: x86: Move TSC offset writes to common code

Also, ensure that the storing of the offset and the reading of the TSC
are never preempted by taking a spinlock.  While the lock is overkill
now, it is useful later in this patch series.

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

1 files changed, 6 insertions, 7 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index d9bec5ee38b8..138746d3afe9 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1146,10 +1146,9 @@ static u64 guest_read_tsc(void)
 }
 
 /*
- * writes 'guest_tsc' into guest's timestamp counter "register"
- * guest_tsc = host_tsc + tsc_offset ==> tsc_offset = guest_tsc - host_tsc
+ * writes 'offset' into guest's timestamp counter offset register
  */
-static void vmx_write_tsc_offset(u64 offset)
+static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
 {
         vmcs_write64(TSC_OFFSET, offset);
 }
@@ -1224,7 +1223,6 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
 {
         struct vcpu_vmx *vmx = to_vmx(vcpu);
         struct shared_msr_entry *msr;
-        u64 host_tsc;
         int ret = 0;
 
         switch (msr_index) {
@@ -1254,8 +1252,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
                 vmcs_writel(GUEST_SYSENTER_ESP, data);
                 break;
         case MSR_IA32_TSC:
-                rdtscll(host_tsc);
-                vmx_write_tsc_offset(data - host_tsc);
+                kvm_write_tsc(vcpu, data);
                 break;
         case MSR_IA32_CR_PAT:
                 if (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PAT) {
@@ -2653,7 +2650,7 @@ 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);
 
-        vmx_write_tsc_offset(0-native_read_tsc());
+        kvm_write_tsc(&vmx->vcpu, 0);
 
         return 0;
 }
@@ -4348,6 +4345,8 @@ static struct kvm_x86_ops vmx_x86_ops = {
         .set_supported_cpuid = vmx_set_supported_cpuid,
 
         .has_wbinvd_exit = cpu_has_vmx_wbinvd_exit,
+
+        .write_tsc_offset = vmx_write_tsc_offset,
 };
 
 static int __init vmx_init(void)