Re: [PATCH v2 0/6] Add TEE based client driver for UEFI Secure Application

[Harshal Dev]

Hi Dmitry,

Gentle Reminder.

Regards,
Harshal

On 21-08-2026 02:04 pm, Harshal Dev wrote:
> Hello Dmitry,
> 
> A gentle reminder. Hopefully we can align on below points and move to
> a v3 of this series.
> 
> Regards,
> Harshal
> 
> On 17-08-2026 11:54 am, Harshal Dev wrote:
>> Hi Dmitry,
>>
>> Many thanks for your engagement and review on this series. I am looking forward
>> to your opinions on below comments so we can align on a a v3 of this series.
>>
>> Best Regards,
>> Harshal
>>
>> On 12-08-2026 05:00 pm, Harshal Dev wrote:
>>> Hi Dmitry,
>>>
>>> On 10-08-2026 12:37 pm, Dmitry Baryshkov wrote:
>>>> On Fri, Jul 24, 2026 at 02:43:42PM +0530, Harshal Dev wrote:
>>>>> Hi Dmitry,
>>>>>
>>>>> On 22-07-2026 01:56 pm, Dmitry Baryshkov wrote:
>>>>>> On Wed, Jul 22, 2026 at 12:29:11PM +0530, Harshal Dev wrote:
>>>>>>> On Qualcomm SoC based platforms, UEFI stores EFI variables within the
>>>>>>> Replay Protected Memory Block (RPMB) which is only accessible by the
>>>>>>> Qualcomm Trusted Execution Environment (QTEE).
>>>>>>
>>>>>> Is it so? I think RPMB is accessible to Linux...
>>>>>
>>>>> I should have been more descriptive here, RPMB is accessible by Linux but
>>>>> its frames can only be prepared by QTEE.
>>>>>
>>>>> The RPMB key which is one-time programmed into the storage controller to allow
>>>>> authentication of the RPMB frames is generated by and only available to a TEE.
>>>>> So on Qualcomm platforms (and many others platforms with a TEE) Linux can only
>>>>> route the RPMB frames generated by QTEE to the storage, it cannot create and
>>>>> write the RPMB frames itself (it doesn't have access to the key).
>>>>>
>>>>> While it is possible for Linux to generate/program/store this key, on Qualcomm
>>>>> platforms we do not want Linux to do so because we do not trust it. We trust
>>>>> QTEE.
>>>>>
>>>>> I will re-phrase this and make it a bit more clear everywhere.
>>>>
>>>> OK.
>>>>
>>>>>
>>>>>>
>>>>>>> For Qualcomm platforms without emulated RPMB support, specifically
>>>>>>
>>>>>> What is emulated RPMB support? Why is it mentioned here? Which platforms
>>>>>> use emulated RPMB?
>>>>>
>>>>> Emulated RPMB refers to RPMB on a storage which doesn't have its own firmware.
>>>>> Primarily, NAND/NOR storage. Unlike UFS/eMMC storage, NAND/NOR storage does not
>>>>> have a storage controller where we can program the RPMB key to be used by the
>>>>> firmware. So we must 'emulate' RPMB by moving the storage driver within QTEE
>>>>> and making the driver hold/use the key.
>>>>>
>>>>> Qualcomm compute SoCs (Glymur, Hamoa) have RPMB available on SPI-*NOR* storage,
>>>>> and a driver for communicating with it is also available in QTEE. And so, these
>>>>> have 'emulated' RPMB.
>>>>
>>>> This needs to be explained in the cover letter.
>>>>
>>>
>>> Ack. 
>>>>>
>>>>> I will add this detail in an updated cover letter.
>>>>>>
>>>>>>> platforms where RPMB is not located within SPI-NOR storage and instead
>>>>>>> located on UFS/EMMC storage, non-volatile EFI variables can only be set via
>>>>>>> a callback request from the UEFI Secure Application to the RPMB service
>>>>>>> running in user-space (within the QTEE supplicant [1]).
>>>>>>
>>>>>> Can it be moved to the kernel?
>>>>>
>>>>> We have a plan to move the RPMB service to the kernel similar to OPTEE:
>>>>> https://elixir.bootlin.com/linux/v7.2-rc3/source/drivers/tee/optee/rpc.c#L449
>>>>>
>>>>> It is a work in progress. Once this happens, we don't need QTEE supplicant available
>>>>> on the Linux distribution.
>>>>
>>>> Ok.
>>>>
>>>>>
>>>>>>
>>>>>>>
>>>>>>> Unlike the QCOM-TEE driver, the QSEECOM driver (used by the current
>>>>>>> QSEECOM based uefisecapp) does not support callback requests.
>>>>>>
>>>>>> How did it work then? I think Windows has been perfectly using QSEECOM
>>>>>> rather than QTEE.
>>>>>
>>>>> It works because Windows on Arm on Qualcomm has SPI-NOR storage. A driver for which
>>>>
>>>> I have WoA devices without SPI NOR. Windows still can store UEFI
>>>> variables.
>>>>
>>>
>>> Ahh, the key point here is 'Windows'. Windows has a separate way of providing
>>> RPMB access via a service in the TrEE driver within the OS:
>>> https://github.com/microsoft/Windows-driver-samples/tree/main/TrEE
>>>
>>> However, the Linux QSEECOM driver we have here in upstream does not have that support.
>>> And so without the QCOMTEE + QTEE supplicant combination, we cannot access EFI
>>> variables on these Qualcomm WoA platforms when they boot with upstream Linux.
>>>
>>>>> is available within QTEE, and so QTEE does not need to make a callback request
>>>>> to Linux to request RPMB frame routing. However, in case of UFS/eMMC storage the
>>>>> driver only exists in the Linux kernel and so QTEE must make a callback request.
>>>>>
>>>>> And so, if you try to use the QSEECOM driver to write EFI-variables to RPMB
>>>>> on a device with UFS/eMMC storage, it won't work.
>>>>
>>>> Yep. It seems to work under Windows though.
>>>>
>>>
>>> As explained above, the mechanism is different for Windows. A different driver
>>> and a different protocol. :)
>>>
>>>>>
>>>>>>
>>>>>>> And on
>>>>>>> certain Qualcomm platforms such as the RB3Gen2, attempts to access the
>>>>>>> QSEECOM interface fail due to lack of support within Qualcomm TEE.
>>>>>>
>>>>>> So, I assume, on RB3 Gen2 the QSEECOM doesn't report uefisecapp as
>>>>>> supported. Does it?
>>>>>
>>>>> It doesn't, this API returns -2 if I add RB3 Gen2 in the allow-list for QSEECOM:
>>>>> https://elixir.bootlin.com/linux/v7.2-rc3/source/drivers/firmware/qcom/qcom_qseecom.c#L46
>>>>
>>>> Does it support QTEE-based uefi variable storage?
>>>>
>>>
>>> It does, the QTEE-based uefi variable storage app, i.e. uefisecapp is loaded by
>>> UEFI on RB3Gen2, however, the QSEECOM interface on RB3Gen2 is broken so it misreports
>>> it as 'not supported'. But the app is loaded and available, which is why if you apply
>>> this patch series, you can communicate with it. Just make sure you take the QTEE
>>> release mentioned in this cover letter.
>>>
>>>>>>> On these platforms, a TEE based uefisecapp client driver is required to:
>>>>>>> 1. Access cached & volatile EFI variables stored in uefisecapp's memory.
>>>>>>> 2. Ensure persistence of non-volatile EFI variables via writes through
>>>>>>> the RPMB service hosted in the QTEE supplicant.
>>>>>>>
>>>>>>> This series introduces such a uefisecapp TEE client driver for the
>>>>>>> aforementioned Qualcomm platforms which installs efi-var operations _if_
>>>>>>> the QCOMTEE driver registers support for an object-IPC based uefisecapp
>>>>>>> service on the TEE bus during its probe. Only new QTEE firmware versions
>>>>>>> available at [2] provide this support.
>>>>>>
>>>>>> What about existing WoA devices?
>>>>>
>>>>> New Windows on Arm devices like Hamoa/Glymur work perfectly fine with existing
>>>>> QSEECOM based uefisecapp. But they will also work with this new QCOMTEE based
>>>>> uefisecapp once they upgrade their firmware.
>>>>
>>>> Do extisting commercial devices suppot it? For example, does Lenovo T14s
>>>> support it? Will it continue to work with this patchset in place?
>>>
>>> Existing devices like the Lenovo T14s do not have mature QCOMTEE/SMCInvoke support
>>> on QTEE side and new QTEE versions for it are not being rolled out. However, this
>>> QCOMTEE based uefisecapp driver and the QSEECOM based uefisecapp driver can co-exist.
>>> It will not cause any breakage of existing working functionality since the QSEECOM
>>> path can probe and continue as usual.
>>>
>>> As per your comments on patch 6 of this series, I plan to enable the QCOMTEE based
>>> uefisecapp as default 'm'. That way we don't need to enable one over the other and
>>> will continue supporting all existing functionality while extending it for devices
>>> with UFS/eMMC storage and running upstream Linux.
>>>
>>> Do let me know your opinion on it.
>>>
>>>>
>>>> What about other existing devices? We have WoA devices starting with
>>>> MSM8998. The QSEECOM driver works on them, but, as you mentioned, it
>>>> can't flash updates to the backing storage.
>>>>
>>>
>>> Unfortunately, unless we roll out new QTEE firmware versions for devices like MSM8998
>>> with QCOMTEE/SMCInvoke support + access to the Uefisecapp over SMCInvoke protocol,
>>> they cannot be helped with this series.
>>>
>>>>> I need to double-check but this firmware release for Glymur on Qualcomm Linux
>>>>> is probably carrying the support for QCOMTEE based uefisecapp access:
>>>>> https://github.com/qualcomm-linux/meta-qcom/commit/728251fcbe5113980805ea6c571e33235062ee71
>>>>> If not, the next release will definitely have it since I have merged support for
>>>>> this in QTEE and talked to the boot firmware release team about this.
>>>>
>>>> Does it work on the CRD?
>>>>
>>>
>>> Yes it does, I have validated on Glymur CRD by locally switching it from the current QSEECOM
>>> based uefisecapp to this new QCOMTEE based uefisecapp. This is the QTEE release which
>>> needs to be consumed for it:
>>> https://github.com/qualcomm-linux/meta-qcom/commit/5590c1dc631827624c110df282965b85ef2a2e60 
>>>
>>>>>
>>>>> The next planned firmware upgrade for Hamoa will also provide this support for
>>>>> Qualcomm Linux. And similarly, for all other targets being supported upstream.
>>>>
>>>> So, we are forcing users to upgrade to the new firmware? That doesn't
>>>> sound nice.
>>>>
>>>
>>> We have an open ecosystem for all devices supported by the Qualcomm Linux distribution,
>>> users can easily consume new releases (and new QTEE versions) to access new features.
>>> Until now, developers/users of RB3Gen2 or IQ-9075 could not access EFI variables to
>>> develop use-cases such as secure-boot key revocation, but by taking this patch series
>>> as part of a subsequent Qualcomm Linux release, they will be able to.
>>>
>>>>>>> Thus, QCOMTEE now maintains a static list of always-available object-IPC
>>>>>>> based secure services exposed by QTEE. These services are implemented either
>>>>>>> within the QTEE kernel or within a pre-loaded Trusted Application (TA)
>>>>>>> usually loaded by the bootloader. The uefisecapp TA is an example of a
>>>>>>> preloaded TA loaded by UEFI. A static list is required since QTEE does not
>>>>>>> yet expose any way to dynamically query and enumerate the services exposed by
>>>>>>> it.
>>>>>>
>>>>>> Can it be fixed instead of having static lists? In the end, we can't
>>>>>> guarantee that users update the firmware.
>>>>>>
>>>>>
>>>>> Unfortunately, no existing QTEE release out there currently has this support.
>>>>> But support for this is currently being added by QTEE team last I checked with them.
>>>>> Once it is available, and a new QTEE firmware release is out there, we will add
>>>>> support for dynamically querying QTEE services in the QCOMTEE driver. 
>>>>
>>>> It seems you are still rolling out QTEE-based support. In such a case,
>>>> please go back and implement dynamic detection of QTEE services.
>>>> Otherwise it would be a nightmare.
>>>>
>>>
>>> We are working on it, but until then there is no overhead involved in maintaining
>>> this static list of services because we don't have to extend/modify this list when
>>> adding support for a new Qualcomm platform upstream. If a particular service from
>>> the list is not implemented/accessible from QTEE we log the event and silently avoid
>>> probing the TEE driver for the service. We also don't add platform specific services
>>> here. So the list doesn't need to be extended on a per-platform basis.
>>>
>>> So unlike the QSEECOM driver, we don't have to keep maintaining this list forever
>>> for all new platforms.
>>>
>>>>>>> To facilitate object-IPC interactions from the kernel-space, this
>>>>>>> series also introduces a tee_client_object_invoke_func() to allow
>>>>>>> invocation of TEE objects similar to the existing tee_client_invoke_func()
>>>>>>> API exported by the TEE subsystem which allows invocation of TEE functions.
>>>>>>> Some suporting changes are also introduced to track and handle operations
>>>>>>> for TEE contexts opened from the kernel-space in the back-end QCOM-TEE
>>>>>>> driver.
>>>>>>>
>>>>>>> Finally and as previously mentioned, access to the object-IPC based uefisecapp
>>>>>>> service is restricted on older QTEE firmware versions. A new QTEE firmware
>>>>>>> release must be picked up from QArtifactory [2] for all upstream supported
>>>>>>> Qualcomm SoCs to enable access to uefisecapp service via the TEE client
>>>>>>> driver.
>>>>>>
>>>>>> What about fused devices?
>>>>>
>>>>> The procedure for updating the firmware on fused devices is slightly different.
>>>>> The firmware images need to be signed by the OEM using the security profile
>>>>> of the chipset before flashing/upgrading them. Security profiles are now public:
>>>>> https://github.com/qualcomm/security-profiles
>>>>
>>>> Will OEMs release new firmware images? What about the devices which are
>>>> already out of the support phase? This whole story rotates about the 'we
>>>> are releasing new firmware with new features' paradigm. However there
>>>> are existing devices in the field, which typically can't be upgraded,
>>>> From your cover letter it seems they can't support UEFI variables
>>>> properly. However they do so in Windows.
>>>>
>>>
>>> Yes Dmitry, this series is effectively forward looking. QSEECOM protocol/driver
>>> support is essentially deprecated on QTEE side, no new features added to QTEE support
>>> it, and it also doesn't work on many devices like the RB3Gen2.
>>>
>>> For existing devices, if they boot with upstream Linux and have RPMB located on
>>> UFS/eMMC this patch series cannot help them. But the focus of this series is not on the
>>> past, it is on currently supported and future hardware. Every new Qualcomm platform
>>> whose support is being up-streamed or is planned to be up-streamed will have access to
>>> EFI variables via this series.
>>>
>>> If someone wants to add support for older Qualcomm devices to access EFI variables
>>> via QSEECOM that patch series will not conflict with this one. Like I said, both
>>> QSEECOM and QCOMTEE based drivers can co-exist.
>>>
>>> Regards,
>>> Harshal
>>>
>>>
>>>  
>>>
>>
>