On Mon, Mar 15, 2021 at 04:13:17PM +1300, Kai Huang wrote:
> On Sun, 14 Mar 2021 17:27:18 +0200 Jarkko Sakkinen wrote:
> > On Sun, Mar 14, 2021 at 05:25:26PM +0200, Jarkko Sakkinen wrote:
> > > On Sat, Mar 13, 2021 at 09:07:36PM +0200, Jarkko Sakkinen wrote:
> > > > On Sat, Mar 13, 2021 at 09:05:36PM +0200, Jarkko Sakkinen wrote:
> > > > > On Fri, Mar 12, 2021 at 01:44:58PM -0800, Sean Christopherson wrote:
> > > > > > On Tue, Mar 09, 2021, Kai Huang wrote:
> > > > > > > Modify sgx_init() to always try to initialize the virtual EPC driver,
> > > > > > > even if the SGX driver is disabled. The SGX 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.
> > > > > > >
> > > > > > > Acked-by: Dave Hansen <dave.hansen@xxxxxxxxx>
> > > > > > > Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx>
> > > > > > > ---
> > > > > > > arch/x86/kernel/cpu/sgx/main.c | 10 +++++++++-
> > > > > > > 1 file changed, 9 insertions(+), 1 deletion(-)
> > > > > > >
> > > > > > > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> > > > > > > index 44fe91a5bfb3..8c922e68274d 100644
> > > > > > > --- a/arch/x86/kernel/cpu/sgx/main.c
> > > > > > > +++ b/arch/x86/kernel/cpu/sgx/main.c
> > > > > > > @@ -712,7 +712,15 @@ static int __init sgx_init(void)
> > > > > > > goto err_page_cache;
> > > > > > > }
> > > > > > >
> > > > > > > - ret = sgx_drv_init();
> > > > > > > + /*
> > > > > > > + * Always try to initialize the native *and* KVM drivers.
> > > > > > > + * The KVM driver is less picky than the native one and
> > > > > > > + * can function if the native one is not supported on the
> > > > > > > + * current system or fails to initialize.
> > > > > > > + *
> > > > > > > + * Error out only if both fail to initialize.
> > > > > > > + */
> > > > > > > + ret = !!sgx_drv_init() & !!sgx_vepc_init();
> > > > > >
> > > > > > I love this code.
> > > > > >
> > > > > > Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> > > > >
> > > > > I'm still wondering why this code let's go through when sgx_drv_init()
> > > > > succeeds and sgx_vepc_init() fails.
> > > > >
> > > > > The inline comment explains only the mirrored case (which does make
> > > > > sense).
> > > >
> > > > I.e. if sgx_drv_init() succeeds, I'd expect that sgx_vepc_init() must
> > > > succeed. Why expect legitly anything else?
> > >
> > > Apologies coming with these ideas at this point, but here is what this
> > > led me.
> > >
> > > I think that the all this complexity comes from a bad code structure.
> > >
> > > So, what is essentially happening here:
> > >
> > > - We essentially want to make EPC always work.
> > > - Driver optionally.
> > >
> > > So what this sums to is something like:
> > >
> > > ret = sgx_epc_init();
> > > if (ret) {
> > > pr_err("EPC initialization failed.\n");
> > > return ret;
> > > }
> > >
> > > ret = sgx_drv_init();
> > > if (ret)
> > > pr_info("Driver could not be initialized.\n");
> > >
> > > /* continue */
> > >
> > > I.e. I think there should be a single EPC init, which does both EPC
> > > bootstrapping and vepc, and driver initialization comes after that.
> >
> > In other words, from SGX point of view, the thing that KVM needs is
> > to cut out EPC and driver part into different islands. How this is now
> > implemented in the current patch set is half-way there but not yet what
> > it should be.
>
> Well conceptually, SGX virtualization and SGX driver are two independently
> functionalities can be enabled separately, although they both requires some
> come functionalities, such as /dev/sgx_provision, which we have moved to
> sgx/main.c exactly for this purpose. THerefore, conceptually, it is bad to make
> assumption that, if SGX virtualization initialization succeeded, SGX driver
> must succeed -- we can potentially add more staff in SGX virtualization in the
> future..
>
> If the name sgx_vepc_init() confuses you, I can rename it to sgx_virt_init().
I don't understand what would be the bad thing here. Can you open that
up please? I'm neither capable of predicting the future...
>
>
> Please let us know if you have comments.
>
/Jarkko
