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From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: linux-sgx@vger.kernel.org
Subject: Re: [PATCH] x86/sgx: Return 0 when !CONFIG_INTEL_SGX_DRIVER
Date: Mon, 12 Aug 2019 18:22:27 -0700
Message-ID: <20190813012227.GJ4996@linux.intel.com> (raw)
In-Reply-To: <20190802193321.llx4dcqhslh46toy@linux.intel.com>

On Fri, Aug 02, 2019 at 10:33:38PM +0300, Jarkko Sakkinen wrote:
> On Thu, Aug 01, 2019 at 09:29:31AM -0700, Sean Christopherson wrote:
> > On Thu, Aug 01, 2019 at 07:22:19PM +0300, Jarkko Sakkinen wrote:
> > > On Mon, Jul 15, 2019 at 06:59:03AM -0700, Sean Christopherson wrote:
> > > > On Sun, Jul 14, 2019 at 05:32:12PM +0300, Jarkko Sakkinen wrote:
> > > > > When the config option is not enabled the initialization is always
> > > > > succesful.
> > > > 
> > > > Why would the be initialization be considered successful?  It's dead code
> > > > and memory consumption if the driver can't load.  When KVM support gets
> > > > added, the initialization can be considered successful if the driver *or*
> > > > virtual EPC are enabled and load cleanly.
> > > 
> > > When a config option disabled means it that the functionality does not
> > > exist at all, which means that there is nothing to fail. That is why it
> > > would be actually better to flag the whole call than the way it is done
> > > in this patch.
> > 
> > Regardless of how it's done, the core SGX management shouldn't consume
> > resources if it doesn't have downstream consumers.  Making INTEL_SGX
> > depend on INTEL_SGX_DRIVER is the obvious alternative.
> 
> Is there a specific blocker that prevents using SGX just with KVM when
> the latter option is disabled?

Nope, KVM does not have any dependencies on the native driver.  But if
sgx_drv_init() returns 0 when CONFIG_INTEL_SGX_DRIVER=n, then sgx_init()
won't handle KVM failure correctly since it will think the native driver
initialized cleanly.  E.g. with both KVM and driver in play, I was
thinking of something like this in sgx_init():

        /* Success if the native *or* virtual driver initialized cleanly. */
        ret = sgx_drv_init();
        ret = sgx_virt_epc_init() ? ret : 0;
        if (ret)
		goto err;

	return 0;

If sgx_drv_init() returns 0 when CONFIG_INTEL_SGX_DRIVER=n, then failure
in sgx_virt_epc_init() is ignored and we end up with the SGX subsystem
wasting resources again.

  reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-14 14:32 Jarkko Sakkinen
2019-07-15  9:29 ` Jarkko Sakkinen
2019-07-15 13:59 ` Sean Christopherson
2019-08-01 16:22   ` Jarkko Sakkinen
2019-08-01 16:29     ` Sean Christopherson
2019-08-02 19:33       ` Jarkko Sakkinen
2019-08-13  1:22         ` Sean Christopherson [this message]
2019-08-15 21:56           ` Jarkko Sakkinen
2019-08-21 17:24             ` Sean Christopherson
2019-08-22  0:29               ` Jarkko Sakkinen
2019-08-22  0:31                 ` Sean Christopherson
2019-08-22 14:42                   ` Jarkko Sakkinen
2019-08-22  1:26                 ` Jarkko Sakkinen

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