Ignore host userspace reads and writes of '0' to PEBS and BTS MSRs that
KVM reports in the MSR-to-save list, but the MSRs are ultimately
unsupported.  All MSRs in said list must be writable by userspace, e.g.
if userspace sends the list back at KVM without filtering out the MSRs it
doesn't need.

Fixes: 8183a538 ("KVM: x86/pmu: Add IA32_DS_AREA MSR emulation to support guest DS")
Fixes: 902caeb6 ("KVM: x86/pmu: Add PEBS_DATA_CFG MSR emulation to support adaptive PEBS")
Fixes: c59a1f10 ("KVM: x86/pmu: Add IA32_PEBS_ENABLE MSR emulation for extended PEBS")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220611005755.753273-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>