KVM: selftests: Remove obsolete and incorrect test case metadata

Delete inaccurate descriptions and obsolete metadata for test cases.
It adds zero value, and has a non-zero chance of becoming stale and
misleading in the future. No functional changes intended.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Like Xu <likexu@tencent.com>
Link: https://lore.kernel.org/r/20230914094803.94661-1-likexu@tencent.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

KVM: selftests: Test disabling NX hugepages on a VM

Add an argument to the NX huge pages test to test disabling the feature
on a VM using the new capability.

Reviewed-by: David Matlack <dmatlack@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20220613212523.3436117-10-bgardon@google.com>
[Handle failure of sudo or setcap more gracefully. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

KVM: selftests: Add NX huge pages test

There's currently no test coverage of NX hugepages in KVM selftests, so
add a basic test to ensure that the feature works as intended.

The test creates a VM with a data slot backed with huge pages. The
memory in the data slot is filled with op-codes for the return
instruction. The guest then executes a series of accesses on the memory,
some reads, some instruction fetches. After each operation, the guest
exits and the test performs some checks on the backing page counts to
ensure that NX page splitting an reclaim work as expected.

Reviewed-by: David Matlack <dmatlack@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20220613212523.3436117-7-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>