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From: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
To: Julien Grall <julien.grall@arm.com>
Cc: "tee-dev@lists.linaro.org" <tee-dev@lists.linaro.org>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>, Wei Liu <wl@xen.org>
Subject: Re: [Xen-devel] [PATCH v6 09/10] tools/arm: tee: add "tee" option for xl.cfg
Date: Tue, 18 Jun 2019 11:19:46 +0000
Message-ID: <87v9x36sz1.fsf@epam.com> (raw)
In-Reply-To: <23dc2135-d9a2-2da1-f302-f53f84fd9cdb@arm.com>


Hi Julien,

Julien Grall writes:

> Hi Volodymyr,
>
> On 6/11/19 7:46 PM, Volodymyr Babchuk wrote:
>> This enumeration controls TEE type for a domain. Currently there is
>> two possible options: either 'none' or 'optee'.
>>
>> 'none' is the default value and it basically disables TEE support at
>> all.
>>
>> 'optee' enables access to the OP-TEE running on a host machine. This
>> requires special OP-TEE build with virtualization support enabled.
>>
>> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
>>
>> ---
>>   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 v5:
>>    - Replaced "native" with "optee" in the commit description.
>>    - Updated and extended documentation based on Julien Grall's
>>      and Ian Jackson's suggestions.
>>
>>   Changes from v4:
>>    - "native" option was replaced with "optee"
>>    - "tee" property was moved from arch-specific section to the
>>       global one. Documentation moved inside "Devices" section.
>>
>>   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    | 21 +++++++++++++++++++++
>>   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, 54 insertions(+)
>>
>> diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
>> index c99d40307e..e65ab6111f 100644
>> --- a/docs/man/xl.cfg.5.pod.in
>> +++ b/docs/man/xl.cfg.5.pod.in
>> @@ -1544,6 +1544,27 @@ Set maximum height for pointer device.
>>     =back
>>   +=item B<tee="STRING">
>> +
>> +B<Arm only.> Set TEE type for the guest. TEE is a Trusted Execution
>> +Environment -- separate secure OS found on some platforms. B<STRING> can be one of the:
>> +
>> +=over 4
>> +
>> +=item B<none>
>> +
>> +Disable TEE support at all. This is the default value.
> How about "Don't allow the guest to use TEE if present on the
> platform. This is the default value.".
I'm perfectly fine with this.

>> +
>> +=item B<optee>
>> +
>> +Allow a guest to use OP-TEE. Note that a virtualization-aware OP-TEE
>> +is required for this. If this option is selected, guest will be able
>
> OOI, what happen if OP-TEE does not support virtualization. Will Xen
> forbid to use it?
Yes, Xen will get an error from OP-TEE during domain construction. This
will lead to domain creation failure.

>> +to access to the real OP-TEE OS running on the host. Guest creation
>
> s/real// it is redundant with the rest of the sentence. However, it
> does not really answer to the question regarding isolation.
Your assumption is correct - OP-TEE provides isolation on its side.

>
>> +will fail if OP-TEE have no resources for a new guest. Number of supported
>> +guests depends on OP-TEE configuration.
>
> How about the following description (correct me if my understanding is
> wrong):
>
> "Allow a guest to access the host OP-TEE OS. Xen will mediate the
> access to OP-TEE and the resource isolation will be provided directly
> by OP-TEE. OP-TEE itself may limit the number of guests that can
> concurrently use it. This requires a virtualization-aware OP-TEE for
> this to work.
>
> This feature is a B<technology preview>."
That's much better than my version. Thank you.

> How can a user know whether OP-TEE supports virtualization? Is it
> configurable at build?
Yes, there is a special configuration option CFG_VIRTUALIZATION. This is
covered in OP-TEE documentation at [1]

[1] https://optee.readthedocs.io/architecture/virtualization.html

-- 
Best regards,Volodymyr Babchuk
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  reply index

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-11 18:46 [Xen-devel] [PATCH v6 00/10] TEE mediator (and OP-TEE) support in XEN Volodymyr Babchuk
2019-06-11 18:46 ` [Xen-devel] [PATCH v6 01/10] xen/arm: add generic TEE mediator framework Volodymyr Babchuk
2019-06-17 16:11   ` Stefano Stabellini
2019-06-11 18:46 ` [Xen-devel] [PATCH v6 02/10] xen/arm: optee: add OP-TEE header files Volodymyr Babchuk
2019-06-15 18:39   ` Julien Grall
2019-06-17 15:24     ` Julien Grall
2019-06-17 16:28       ` Stefano Stabellini
2019-06-17 16:34         ` Julien Grall
2019-06-17 17:28           ` Stefano Stabellini
2019-06-19  8:20             ` Lars Kurth
2019-06-19 10:26               ` Julien Grall
2019-06-11 18:46 ` [Xen-devel] [PATCH v6 03/10] xen/arm: optee: add OP-TEE mediator skeleton Volodymyr Babchuk
2019-06-19 11:01   ` Julien Grall
2019-06-19 11:03     ` Julien Grall
2019-06-19 15:44       ` Volodymyr Babchuk
2019-06-11 18:46 ` [Xen-devel] [PATCH v6 04/10] xen/arm: optee: add fast calls handling Volodymyr Babchuk
2019-06-11 18:46 ` [Xen-devel] [PATCH v6 05/10] xen/arm: optee: add std call handling Volodymyr Babchuk
2019-06-11 18:46 ` [Xen-devel] [PATCH v6 06/10] xen/arm: optee: add support for RPC SHM buffers Volodymyr Babchuk
2019-06-11 18:46 ` [Xen-devel] [PATCH v6 07/10] xen/arm: optee: add support for arbitrary shared memory Volodymyr Babchuk
2019-06-11 18:46 ` [Xen-devel] [PATCH v6 08/10] xen/arm: optee: add support for RPC commands Volodymyr Babchuk
2019-06-11 18:46 ` [Xen-devel] [PATCH v6 09/10] tools/arm: tee: add "tee" option for xl.cfg Volodymyr Babchuk
2019-06-15 19:10   ` Julien Grall
2019-06-18 11:19     ` Volodymyr Babchuk [this message]
2019-06-18 12:49       ` Julien Grall
2019-06-18 14:30         ` Volodymyr Babchuk
2019-06-18 15:19           ` Julien Grall
2019-06-18 15:23             ` Volodymyr Babchuk
2019-06-19 10:30               ` Julien Grall
2019-06-11 18:46 ` [Xen-devel] [PATCH v6 10/10] tools/arm: optee: create optee firmware node in DT if tee=optee Volodymyr Babchuk
2019-06-19 11:08 ` [Xen-devel] [PATCH v6 00/10] TEE mediator (and OP-TEE) support in XEN Julien Grall

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