KVM: VMX: Always reflect SGX EPCM #PFs back into the guest

KVM: VMX: Always reflect SGX EPCM #PFs back into the guest

When handling intercepted #PFs, reflect EPCM (Enclave Page Cache Map)
violations, i.e. #PFs with the SGX flag set, back into the guest.  KVM
doesn't shadow EPCM entries (the EPCM deals only with virtual/linear
addresses), and so EPCM violation cannot be due to KVM interference,
and more importantly can't be resolved by KVM.

On pre-SGX2 hardware, EPCM violations are delivered as #GP(0) faults, but
on SGX2+ hardware, they are delivered as #PF(SGX).  Failure to account for
the SGX2 behavior could put a vCPU into an infinite loop due to KVM not
realizing the #PF is the guest's responsibility.

Take care to deliver the EPCM violation as a #GP(0) if the _guest_ CPU
model is only SGX1.

Fixes: 72add915fbd5 ("KVM: VMX: Enable SGX virtualization for SGX1, SGX2 and LC")
Cc: Kai Huang <kai.huang@intel.com>
Reviewed-by: Richard Lyu <richard.lyu@suse.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://patch.msgid.link/20251121222018.348987-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>