RE: [PATCH v5 04/15] soc: qcom: ice: add hwkm support in ice

["Gaurav Kashyap (QUIC)" <quic_gaurkash@quicinc.com>]

On 06/19/2024 12:12 AM PDT, Neil Armstrong wrote:
> Le 19/06/2024 à 00:08, Gaurav Kashyap (QUIC) a écrit :
> > Hello Neil,
> >
> > On 06/18/2024 12:14 AM PDT, Neil Armstrong wrote:
> >> On 17/06/2024 02:50, Gaurav Kashyap wrote:
> >>> Qualcomm's ICE (Inline Crypto Engine) contains a proprietary key
> >>> management hardware called Hardware Key Manager (HWKM).
> >>> This patch integrates HWKM support in ICE when it is available. HWKM
> >>> primarily provides hardware wrapped key support where the ICE
> >>> (storage) keys are not available in software and protected in
> >>> hardware.
> >>>
> >>> When HWKM software support is not fully available (from Trustzone),
> >>> there can be a scenario where the ICE hardware supports HWKM, but it
> >>> cannot be used for wrapped keys. In this case, standard keys have to
> >>> be used without using HWKM. Hence, providing a toggle controlled by
> >>> a devicetree entry to use HWKM or not.
> >>>
> >>> Tested-by: Neil Armstrong <neil.armstrong@linaro.org>
> >>> Signed-off-by: Gaurav Kashyap <quic_gaurkash@quicinc.com>
> >>> ---
> >>>    drivers/soc/qcom/ice.c | 153
> >> +++++++++++++++++++++++++++++++++++++++--
> >>>    include/soc/qcom/ice.h |   1 +
> >>>    2 files changed, 150 insertions(+), 4 deletions(-)
> >>>
> >>> diff --git a/drivers/soc/qcom/ice.c b/drivers/soc/qcom/ice.c index
> >>> 6f941d32fffb..d5e74cf2946b 100644
> >>> --- a/drivers/soc/qcom/ice.c
> >>> +++ b/drivers/soc/qcom/ice.c
> >>> @@ -26,6 +26,40 @@
> >>
> >> <snip>
> >>
> >>> +
> >>>    static struct qcom_ice *qcom_ice_create(struct device *dev,
> >>>                                        void __iomem *base)
> >>>    {
> >>> @@ -239,6 +382,8 @@ static struct qcom_ice *qcom_ice_create(struct
> >> device *dev,
> >>>                engine->core_clk = devm_clk_get_enabled(dev, NULL);
> >>>        if (IS_ERR(engine->core_clk))
> >>>                return ERR_CAST(engine->core_clk);
> >>> +     engine->use_hwkm = of_property_read_bool(dev->of_node,
> >>> +                                              "qcom,ice-use-hwkm");
> >>
> >> Please drop this property and instead add an scm function calling:
> >>
> >> __qcom_scm_is_call_available(QCOM_SCM_SVC_ES,
> >> QCOM_SCM_ES_DERIVE_SW_SECRET)
> >>
> >> like
> >>
> >> bool qcom_scm_derive_sw_secret_available(void)
> >> {
> >>          if (!__qcom_scm_is_call_available(__scm->dev,
> QCOM_SCM_SVC_ES,
> >>                                            QCOM_SCM_ES_DERIVE_SW_SECRET))
> >>                  return false;
> >>
> >>          return true;
> >> }
> >>
> >> You may perhaps only call qcom_scm_derive_sw_secret_available() for
> >> some ICE versions.
> >>
> >> Neil
> >
> > The issue here is that for the same ICE version, based on the chipset,
> > there might be different configurations.
> 
> So use a combination of a list of compatible strings +
> qcom_scm_derive_sw_secret_available()
> to enable hwkm.
> 
> Neil
>

Okay, that makes sense to me, I will try that.
In fact, looking for only QCOM_SCM_ES_GENERATE_ICE_KEY instead of SW_SECRET works better.
And would work even without compatible strings.
As availability of QCOM_SCM_ES_GENERATE_ICE_KEY will correlate with TZ/firmware having the necessary support.

> >
> > Is it acceptable to use the addressable size from DTSI instead?
> > Meaning, if it 0x8000, it would take the legacy route, and only when
> > it has been updated to 0x10000, we would use HWKM and wrapped keys.
> >
> >>
> >>>
> >>>        if (!qcom_ice_check_supported(engine))
> >>>                return ERR_PTR(-EOPNOTSUPP); diff --git
> >>> a/include/soc/qcom/ice.h b/include/soc/qcom/ice.h index
> >>> 9dd835dba2a7..1f52e82e3e1c 100644
> >>> --- a/include/soc/qcom/ice.h
> >>> +++ b/include/soc/qcom/ice.h
> >>> @@ -34,5 +34,6 @@ int qcom_ice_program_key(struct qcom_ice *ice,
> >>>                         const struct blk_crypto_key *bkey,
> >>>                         u8 data_unit_size, int slot);
> >>>    int qcom_ice_evict_key(struct qcom_ice *ice, int slot);
> >>> +bool qcom_ice_hwkm_supported(struct qcom_ice *ice);
> >>>    struct qcom_ice *of_qcom_ice_get(struct device *dev);
> >>>    #endif /* __QCOM_ICE_H__ */
> >
> > Regards,
> > Gaurav

Regards,
Gaurav