Revert "KVM: nVMX: Expose load IA32_PERF_GLOBAL_CTRL VM-{Entry,Exit} control"

Revert "KVM: nVMX: Expose load IA32_PERF_GLOBAL_CTRL VM-{Entry,Exit} control"

This reverts commit a73bf9486e93da01511009a652c1cdf73f9cd893.

Since commit a73bf9486e93 ("KVM: nVMX: Expose load IA32_PERF_GLOBAL_CTRL
VM-{Entry,Exit} control"), KVM has taken ownership of the "load
IA32_PERF_GLOBAL_CTRL" VMX entry/exit control bits, trying to set these
bits in the IA32_VMX_TRUE_{ENTRY,EXIT}_CTLS MSRs if the guest's CPUID
supports the architectural PMU (CPUID[EAX=0Ah].EAX[7:0]=1), and clear
otherwise.

This was a misguided attempt at mimicking what commit 0ac421831741
("KVM: nVMX: Do not expose MPX VMX controls when guest MPX disabled",
2018-10-01) did for MPX.  However, that commit was a workaround for
another KVM bug and not something that should be imitated.  Mucking with
the VMX MSRs creates a subtle, difficult to maintain ABI as KVM must
ensure that any internal changes, e.g. to how KVM handles _any_ guest
CPUID changes, yield the same functional result.  Therefore, KVM's policy
is to let userspace have full control of the guest vCPU model so long
as the host kernel is not at risk.

Now that KVM really truly ensures kvm_set_msr() will succeed by loading
PERF_GLOBAL_CTRL if and only if it exists, revert KVM's misguided and
roundabout behavior.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[sean: make it a pure revert]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220722224409.1336532-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>