KVM: x86: Restrict get_mt_mask() to a u8, use KVM_X86_OP_OPTIONAL_RET0
Restrict get_mt_mask() to a u8 and reintroduce using a RET0 static_call
for the SVM implementation. EPT stores the memtype information in the
lower 8 bits (bits 6:3 to be precise), and even returns a shifted u8
without an explicit cast to a larger type; there's no need to return a
full u64.
Note, RET0 doesn't play nice with a u64 return on 32-bit kernels, see
commit
bf07be36cd88 ("KVM: x86: do not use KVM_X86_OP_OPTIONAL_RET0 for
get_mt_mask").
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <
20220714153707.
3239119-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>