SVM already has specific handlers of MSR_IA32_DEBUGCTLMSR in the
svm_get/set_msr, so the x86 common part can be safely moved to VMX.
This allows KVM to store the bits it supports in GUEST_IA32_DEBUGCTL.

Add vmx_supported_debugctl() to refactor the throwing logic of #GP.
Signed-off-by: NLike Xu <like.xu@linux.intel.com>
Reviewed-by: NAndi Kleen <ak@linux.intel.com>
Message-Id: <20210108013704.134985-2-like.xu@linux.intel.com>
[Merge parts of Chenyi Qiang's "KVM: X86: Expose bus lock debug exception
 to guest". - Paolo]
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>