Re: [PATCH v38 14/24] x86/sgx: Add SGX_IOC_ENCLAVE_INIT

[Borislav Petkov]

On Mon, Sep 21, 2020 at 11:10:21AM -0700, Sean Christopherson wrote:
> The LE pubkey hash MSRs are special snowflakes.  They get reset to Intel's
> default key on any loss of EPC, e.g. if the system does a suspend/resume
> cycle.  The approach we took (obviously) is to assume the kernel's cache can
> be stale at any given time.  The alternative would be to try and track loss
> of EPC conditions and emulate the reset, but that's a bit dicey on bare
> metal as any missed case would hose SGX, and in a VM it's theoretically
> impossible to handle as a particularly unhelpful VMM could emulate loss of
> EPC at will.

Lemme try to understand this: the system could suspend/resume right
here:

        sgx_update_lepubkeyhash_msrs(lepubkeyhash, false);

<--- suspend/resume

        ret = __einit(sigstruct, token, sgx_get_epc_addr(secs));

and thus the MSRs would have the default key so you'd need the second
__einit() call?

But what happens if the system suspends before the second __einit()
call?

Why don't you simply drop that @enforce param and let the caller handle
any retries?

Or is the scenario something different?

Or you could perhaps disable suspend/resume around it, maybe something
like lock_system_sleep() or so, from a quick grep...

> Yes, this need a big fat comment.

Oh yeah.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette