Re: [Xen-devel] [PATCH v4 09/10] tools/arm: tee: add "tee" option for xl.cfg

[Achin Gupta <Achin.Gupta@xxxxxxx>]

Hi Julien,

On Mon, Mar 18, 2019 at 03:49:12PM +0000, Julien Grall wrote:
> (+ Achin)
>
> On 07/03/2019 21:04, Volodymyr Babchuk wrote:
> > From: Volodymyr Babchuk <vlad.babchuk@xxxxxxxxx>
> >
> > This enumeration controls TEE type for a domain. Currently there is
> > two possible options: either 'none' or 'native'.
> >
> > 'none' is the default value and it basically disables TEE support at
> > all.
> >
> > 'native' enables access to a "real" TEE installed on a platform.
>
> I am aware I made that suggestion. But I think the naming is not ideal
> between the user and the toolstack. The question is how this is going to fit
> with the S-EL2 feature where multiple TEE can run together?
>
> I have CCed Achin to see he has any vision how this could be interfaced.

Thanks.

Multiple TEEs (or rather Trusted OSs) can coexist on Armv8.3 and earlier. They
will not be isolated but play along nicely.

The intent is that prior to S-EL2 and multiple TOSs, each TOS will migrate to
using the SPCI spec. At this stage, there should be no need for a TOS specific
mediator in the Hypervisor. IOW, there should be a "generic" SPCI
mediator. Maybe, we can add a TEE type 'generic' later to enable access to any
TEE through this generic interface?

Support for multiple TOSs has raised other questions that we are trying to
address e.g. dependencies between them or on guests in Nwd, impact on scheduling
decisions made by Nwd etc. Support for OP-TEE in this patch stack does not need
to answer these just yet it seems. It is more likely that we will have to tackle
support for multiple TEEs afresh rather than treating it as an extension of
support for a specific TOS.

Happy to discuss further and I hope this helps in some way.

cheers,
Achin


>
> >
> > It is possible to add another types in the future.
> >
> > Signed-off-by: Volodymyr Babchuk <vlad.babchuk@xxxxxxxxx>
> > ---
> >
> >   All the patches to optee.c should be merged together. They were
> >   split to ease up review. But they depend heavily on each other.
> >
> >   Changes from v3:
> >    - tee_enabled renamed to tee_type. Currently two types are supported
> >      as described in the commit message
> >    - Add LIBXL_HAVE_BUILDINFO_ARCH_ARM_TEE definition
> >
> >   Changes from v2:
> >    - Use arch.tee_enabled instead of separate domctl
> > ---
> >   docs/man/xl.cfg.5.pod.in    | 12 ++++++++++++
> >   tools/libxl/libxl.h         |  5 +++++
> >   tools/libxl/libxl_arm.c     | 13 +++++++++++++
> >   tools/libxl/libxl_types.idl |  6 ++++++
> >   tools/xl/xl_parse.c         |  9 +++++++++
> >   5 files changed, 45 insertions(+)
> >
> > diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
> > index ad81af1ed8..e15981882b 100644
> > --- a/docs/man/xl.cfg.5.pod.in
> > +++ b/docs/man/xl.cfg.5.pod.in
> > @@ -2702,6 +2702,18 @@ Currently, only the "sbsa_uart" model is supported 
> > for ARM.
> >   =back
> > +=over 4
> > +
> > +=item B<tee=["none", "native"]>
> > +
> > +Set TEE type for the guest. Currently only OP-TEE is supported. If
> > +this option is set to "native", xl will create guest, which can access
> > +native TEE on your system (just make sure that you are using OP-TEE
> > +with virtualization support endabled). Also OP-TEE node will be
> > +emitted into guest's device tree.
> > +
> > +=back
> > +
> >   =head3 x86
> >   =over 4
> > diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
> > index a38e5cdba2..b24e4141b1 100644
> > --- a/tools/libxl/libxl.h
> > +++ b/tools/libxl/libxl.h
> > @@ -273,6 +273,11 @@
> >    */
> >   #define LIBXL_HAVE_BUILDINFO_ARM_GIC_VERSION 1
> > +/*
> > + * libxl_domain_build_info has the arch_arm.tee field.
> > + */
> > +#define LIBXL_HAVE_BUILDINFO_ARCH_ARM_TEE 1
> > +
> >   /*
> >    * LIBXL_HAVE_SOFT_RESET indicates that libxl supports performing
> >    * 'soft reset' for domains and there is 'soft_reset' shutdown reason
> > diff --git a/tools/libxl/libxl_arm.c b/tools/libxl/libxl_arm.c
> > index 141e159043..6930d0ab3b 100644
> > --- a/tools/libxl/libxl_arm.c
> > +++ b/tools/libxl/libxl_arm.c
> > @@ -89,6 +89,19 @@ int libxl__arch_domain_prepare_config(libxl__gc *gc,
> >           return ERROR_FAIL;
> >       }
> > +    switch (d_config->b_info.arch_arm.tee) {
> > +    case LIBXL_TEE_TYPE_NONE:
> > +        config->arch.tee_type = XEN_DOMCTL_CONFIG_TEE_NONE;
> > +        break;
> > +    case LIBXL_TEE_TYPE_NATIVE:
> > +        config->arch.tee_type = XEN_DOMCTL_CONFIG_TEE_NATIVE;
> > +        break;
> > +    default:
> > +        LOG(ERROR, "Unknown TEE type %d",
> > +            d_config->b_info.arch_arm.tee);
> > +        return ERROR_FAIL;
> > +    }
> > +
> >       return 0;
> >   }
> > diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
> > index b685ac47ac..4f1eb229b8 100644
> > --- a/tools/libxl/libxl_types.idl
> > +++ b/tools/libxl/libxl_types.idl
> > @@ -457,6 +457,11 @@ libxl_gic_version = Enumeration("gic_version", [
> >       (0x30, "v3")
> >       ], init_val = "LIBXL_GIC_VERSION_DEFAULT")
> > +libxl_tee_type = Enumeration("tee_type", [
> > +    (0, "none"),
> > +    (1, "native")
> > +    ], init_val = "LIBXL_TEE_TYPE_NONE")
> > +
> >   libxl_rdm_reserve = Struct("rdm_reserve", [
> >       ("strategy",    libxl_rdm_reserve_strategy),
> >       ("policy",      libxl_rdm_reserve_policy),
> > @@ -615,6 +620,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
> >       ("arch_arm", Struct(None, [("gic_version", libxl_gic_version),
> >                                  ("vuart", libxl_vuart_type),
> > +                               ("tee",  libxl_tee_type),
>
> AFAICT, TEE also exists on other architecture. So I am wondering whether
> this field should be moved out of arch_arm?
>
> Cheers,
>
> --
> Julien Grall

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