Re: [PATCH 4/4] x86/sgx: Implement ENCLS[EUPDATESVN] and opportunistically call it during first EPC page alloc

[Jarkko Sakkinen <jarkko@kernel.org>]

On Fri, Mar 28, 2025 at 08:27:51AM +0000, Reshetova, Elena wrote:
> 
> > On Thu, Mar 27, 2025 at 03:42:30PM +0000, Reshetova, Elena wrote:
> > > > > > > +	case SGX_NO_UPDATE:
> > > > > > > +		pr_debug("EUPDATESVN was successful, but CPUSVN
> > was not
> > > > > > updated, "
> > > > > > > +			"because current SVN was not newer than
> > > > > > CPUSVN.\n");
> > > > > > > +		break;
> > > > > > > +	case SGX_EPC_NOT_READY:
> > > > > > > +		pr_debug("EPC is not ready for SVN update.");
> > > > > > > +		break;
> > > > > > > +	case SGX_INSUFFICIENT_ENTROPY:
> > > > > > > +		pr_debug("CPUSVN update is failed due to Insufficient
> > > > > > entropy in RNG, "
> > > > > > > +			"please try it later.\n");
> > > > > > > +		break;
> > > > > > > +	case SGX_EPC_PAGE_CONFLICT:
> > > > > > > +		pr_debug("CPUSVN update is failed due to
> > concurrency
> > > > > > violation, please "
> > > > > > > +			"stop running any other ENCLS leaf and try it
> > > > > > later.\n");
> > > > > > > +		break;
> > > > > > > +	default:
> > > > > > > +		break;
> > > > > >
> > > > > > Remove pr_debug() statements.
> > > > >
> > > > > This I am not sure it is good idea. I think it would be useful for system
> > > > > admins to have a way to see that update either happened or not.
> > > > > It is true that you can find this out by requesting a new SGX attestation
> > > > > quote (and see if newer SVN is used), but it is not the faster way.
> > > >
> > > > Maybe pr_debug() is them wrong level if they are meant for sysadmins?
> > > >
> > > > I mean these should not happen in normal behavior like ever? As
> > > > pr_debug() I don't really grab this.
> > >
> > > SGX_NO_UPDATE will absolutely happen normally all the time.
> > > Since EUPDATESVN is executed every time EPC is empty, this is the
> > > most common code you will get back (because microcode updates are rare).
> > > Others yes, that would indicate some error condition.
> > > So, what is the pr_level that you would suggest?
> > 
> > Right, got it. That changes my conclusions:
> > 
> > So I'd reformulate it like:
> > 
> > 	switch (ret) {
> > 	case 0:
> > 		pr_info("EUPDATESVN: success\n);
> > 		break;
> > 	case SGX_EPC_NOT_READY:
> > 	case SGX_INSUFFICIENT_ENTROPY:
> > 	case SGX_EPC_PAGE_CONFLICT:
> > 		pr_err("EUPDATESVN: error %d\n", ret);
> > 		/* TODO: block/teardown driver? */
> > 		break;
> > 	case SGX_NO_UPDATE:
> > 		break;
> > 	default:
> > 		pr_err("EUPDATESVN: unknown error %d\n", ret);
> > 		/* TODO: block/teardown driver? */
> > 		break;
> > 	}
> > 
> > Since when this is executed EPC usage is zero error cases should block
> > or teardown SGX driver, presuming that they are because of either
> > incorrect driver state or spurious error code.
> 
> I agree with the above, but not sure at all about the blocking/teardown the
> driver. They are all potentially temporal things and  SGX_INSUFFICIENT_ENTROPY
> is even outside of SGX driver control and *does not* indicate any error
> condition on the driver side itself. SGX_EPC_NOT_READY and SGX_EPC_PAGE_CONFLICT
> would mean we have a bug somewhere because we thought we could go
> do EUDPATESVN on empty EPC and prevented anyone from creating
> pages in meanwhile but looks like we missed smth. That said, I dont know if we
> want to fail the whole system in case we have such a code bug, this is very 
> aggressive (in case it is some rare edge condition that no one knew about or
> guessed). So, I would propose to print the pr_err() as you have above but
> avoid destroying the driver. 
> Would this work? 

I think now is the time that you should really roll out a new version in
the way you see fit and we will revisit that.

I already grabbed from your example that I got some of the error codes
horribly wrong :-) Still I think the draft of error planning I put is
at least towards right direction.

> 
> Best Regards,
> Elena.
> 
> 
> > 
> > If this happens, we definitely do not want service, right?
> > 
> > I'm not sure of all error codes how serious they are, or are all of them
> > consequence of incorrectly working driver.
> > 
> > BR, Jarkko

BR, Jarkko