x86,kvm,vmx: Don't trap writes to CR4.TSD

CR4.TSD is guest-owned; don't trap writes to it in VMX guests.  This
avoids a VM exit on context switches into or out of a PR_TSC_SIGSEGV
task.

I think that this fixes an unintentional side-effect of:
    4c38609ac569 KVM: VMX: Make guest cr4 mask more conservative

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx.c

@@ -105,7 +105,7 @@ module_param(nested, bool, S_IRUGO);
 	(KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST | X86_CR0_PG | X86_CR0_PE)
 #define KVM_CR4_GUEST_OWNED_BITS				      \
 	(X86_CR4_PVI | X86_CR4_DE | X86_CR4_PCE | X86_CR4_OSFXSR      \
-	 | X86_CR4_OSXMMEXCPT)
+	 | X86_CR4_OSXMMEXCPT | X86_CR4_TSD)
 
 #define KVM_PMODE_VM_CR4_ALWAYS_ON (X86_CR4_PAE | X86_CR4_VMXE)
 #define KVM_RMODE_VM_CR4_ALWAYS_ON (X86_CR4_VME | X86_CR4_PAE | X86_CR4_VMXE)