Re: [PATCH v3] KVM: nVMX: Advertise ENCLS_EXITING to L1 iff SGX is fully supported

[Sean Christopherson <seanjc@google.com>]

On Wed, Oct 26, 2022, Emanuele Giuseppe Esposito wrote:
> Clear enable_sgx if ENCLS-exiting is not supported, i.e. if SGX cannot be
> virtualized.  This fixes a bug where KVM would advertise ENCLS-exiting to
> L1 and propagate the control from vmcs12 to vmcs02 even if ENCLS-exiting
> isn't supported in secondary execution controls, e.g. because SGX isn't
> fully enabled, and thus induce an unexpected VM-Fail in L1.
> 
> Not updating enable_sgx is responsible for a second bug:
> vmx_set_cpu_caps() doesn't clear the SGX bits when hardware support is
> unavailable.  This is a much less problematic bug as it only pops up
> if SGX is soft-disabled (the case being handled by cpu_has_sgx()) or if
> SGX is supported for bare metal but not in the VMCS (will never happen
> when running on bare metal, but can theoertically happen when running in
> a VM).
> 
> Last but not least, KVM should ideally have module params reflect KVM's
> actual configuration.
> 
> RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=2127128
> 
> Fixes: 72add915fbd5 ("KVM: VMX: Enable SGX virtualization for SGX1, SGX2 and LC")
> Cc: stable@vger.kernel.org
> 
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Suggested-by: Bandan Das <bsd@redhat.com>
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
> ---

Reviewed-by: Sean Christopherson <seanjc@google.com>