On Tue, 2021-03-02 at 18:53 +0100, Boris Petkov wrote:

On March 2, 2021 5:02:13 PM GMT+01:00, Sean Christopherson [off-list ref] wrote:

quoted

The KVM use case is to query /proc/cpuinfo to see if sgx2 can be
enabled in a
guest.

You mean before the guest ia created? I sure hope there's a better way to query HV-supported features than grepping /proc/cpuinfo...

quoted

The counter-argument to that is we might want sgx2 in /proc/cpuinfo to
mean sgx2
is enabled in hardware _and_ supported by the kernel.  Userspace can
grep for
sgx in /proc/cpuinfo, and use cpuid to discover sgx2, so it's not a
blocker.

Question is, what exactly that flag should denote: that EDMM is supported in the HV and guests can do the dynamic thing of adding/rwmoving EPC pages? Is that the only feature behind SGX2?

Yes SGX2 == EDMM. Other sub-features, such as VMM oversubscription, have other CPUID
bits.

quoted

That being said, adding some form of capability/versioning to SGX seems
inevitable, not sure it's worth witholding sgx2 from /proc/cpuinfo.

See what I typed earlier - no objections from me if a proper use case is identified and written down.

Thx.