Re: [RFC PATCH v3 08/27] x86/sgx: Initialize virtual EPC driver even when SGX driver is disabled

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On Tue, Feb 02, 2021, Jarkko Sakkinen wrote:
> On Mon, Feb 01, 2021 at 06:40:40PM +1300, Kai Huang wrote:
> > On Sat, 30 Jan 2021 16:45:43 +0200 Jarkko Sakkinen wrote:
> > > On Tue, Jan 26, 2021 at 10:31:00PM +1300, Kai Huang wrote:
> > > > Modify sgx_init() to always try to initialize the virtual EPC driver,
> > > > even if the bare-metal SGX driver is disabled.  The bare-metal driver
> > > > might be disabled if SGX Launch Control is in locked mode, or not
> > > > supported in the hardware at all.  This allows (non-Linux) guests that
> > > > support non-LC configurations to use SGX.
> > > > 
> > > > Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx>
> > > > ---
> > > > v2->v3:
> > > > 
> > > >  - Changed from sgx_virt_epc_init() to sgx_vepc_init().
> > > > 
> > > > ---
> > > >  arch/x86/kernel/cpu/sgx/main.c | 4 +++-
> > > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> > > > index 21c2ffa13870..93d249f7bff3 100644
> > > > --- a/arch/x86/kernel/cpu/sgx/main.c
> > > > +++ b/arch/x86/kernel/cpu/sgx/main.c
> > > > @@ -12,6 +12,7 @@
> > > >  #include "driver.h"
> > > >  #include "encl.h"
> > > >  #include "encls.h"
> > > > +#include "virt.h"
> > > >  
> > > >  struct sgx_epc_section sgx_epc_sections[SGX_MAX_EPC_SECTIONS];
> > > >  static int sgx_nr_epc_sections;
> > > > @@ -712,7 +713,8 @@ static int __init sgx_init(void)
> > > >  		goto err_page_cache;
> > > >  	}
> > > >  
> > > > -	ret = sgx_drv_init();
> > > > +	/* Success if the native *or* virtual EPC driver initialized cleanly. */
> > > > +	ret = !!sgx_drv_init() & !!sgx_vepc_init();
> > > 
> > > If would create more dumb code and just add
> > > 
> > > ret = sgx_vepc_init()
> > > if (ret)
> > >         goto err_kthread;
> > 
> > Do you mean you want below?
> > 
> > 	ret = sgx_drv_init();
> > 	ret = sgx_vepc_init();
> > 	if (ret)
> > 		goto err_kthread;
> > 
> > This was Sean's original code, but Dave didn't like it.
> 
> I think it should be like:
> 
> ret = sgx_drv_init();
> if (ret)
>         pr_warn("Driver initialization failed with %d\n", ret);
> 
> ret = sgx_vepc_init();
> if (ret)
> 	goto err_kthread;

And that's wrong, it doesn't correctly handle the case where sgx_drv_init()
succeeds but sgx_vepc_init() fails.

> There is problem here anyhow. I.e. -ENODEV's from sgx_drv_init().  I think
> how driver.c should be changed would be just to return 0 in the places
> where it now return -ENODEV. Consider "not initialized" as a successful
> initialization.





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