Re: [PATCH v6 09/17] soc: qcom: ice: add HWKM support to the ICE driver

[Dmitry Baryshkov]

On Mon, Sep 09, 2024 at 10:58:30AM GMT, Neil Armstrong wrote:
> On 07/09/2024 00:07, Dmitry Baryshkov wrote:
> > On Fri, Sep 06, 2024 at 08:07:12PM GMT, Bartosz Golaszewski wrote:
> > > From: Gaurav Kashyap <quic_gaurkash@xxxxxxxxxxx>
> > > 
> > > Qualcomm's ICE (Inline Crypto Engine) contains a proprietary key
> > > management hardware called Hardware Key Manager (HWKM). Add HWKM support
> > > to the ICE driver if it is available on the platform. HWKM primarily
> > > provides hardware wrapped key support where the ICE (storage) keys are
> > > not available in software and instead 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, raw keys have to be used without
> > > using the HWKM. We query the TZ at run-time to find out whether wrapped
> > > keys support is available.
> > > 
> > > Tested-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
> > > Signed-off-by: Gaurav Kashyap <quic_gaurkash@xxxxxxxxxxx>
> > > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> > > ---
> > >   drivers/soc/qcom/ice.c | 152 +++++++++++++++++++++++++++++++++++++++++++++++--
> > >   include/soc/qcom/ice.h |   1 +
> > >   2 files changed, 149 insertions(+), 4 deletions(-)
> > > 
> > >   int qcom_ice_enable(struct qcom_ice *ice)
> > >   {
> > > +	int err;
> > > +
> > >   	qcom_ice_low_power_mode_enable(ice);
> > >   	qcom_ice_optimization_enable(ice);
> > > -	return qcom_ice_wait_bist_status(ice);
> > > +	if (ice->use_hwkm)
> > > +		qcom_ice_enable_standard_mode(ice);
> > > +
> > > +	err = qcom_ice_wait_bist_status(ice);
> > > +	if (err)
> > > +		return err;
> > > +
> > > +	if (ice->use_hwkm)
> > > +		qcom_ice_hwkm_init(ice);
> > > +
> > > +	return err;
> > >   }
> > >   EXPORT_SYMBOL_GPL(qcom_ice_enable);
> > > @@ -150,6 +282,10 @@ int qcom_ice_resume(struct qcom_ice *ice)
> > >   		return err;
> > >   	}
> > > +	if (ice->use_hwkm) {
> > > +		qcom_ice_enable_standard_mode(ice);
> > > +		qcom_ice_hwkm_init(ice);
> > > +	}
> > >   	return qcom_ice_wait_bist_status(ice);
> > >   }
> > >   EXPORT_SYMBOL_GPL(qcom_ice_resume);
> > > @@ -157,6 +293,7 @@ EXPORT_SYMBOL_GPL(qcom_ice_resume);
> > >   int qcom_ice_suspend(struct qcom_ice *ice)
> > >   {
> > >   	clk_disable_unprepare(ice->core_clk);
> > > +	ice->hwkm_init_complete = false;
> > >   	return 0;
> > >   }
> > > @@ -206,6 +343,12 @@ int qcom_ice_evict_key(struct qcom_ice *ice, int slot)
> > >   }
> > >   EXPORT_SYMBOL_GPL(qcom_ice_evict_key);
> > > +bool qcom_ice_hwkm_supported(struct qcom_ice *ice)
> > > +{
> > > +	return ice->use_hwkm;
> > > +}
> > > +EXPORT_SYMBOL_GPL(qcom_ice_hwkm_supported);
> > > +
> > >   static struct qcom_ice *qcom_ice_create(struct device *dev,
> > >   					void __iomem *base)
> > >   {
> > > @@ -240,6 +383,7 @@ 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 = qcom_scm_has_wrapped_key_support();
> > 
> > This still makes the decision on whether to use HW-wrapped keys on
> > behalf of a user. I suppose this is incorrect. The user must be able to
> > use raw keys even if HW-wrapped keys are available on the platform. One
> > of the examples for such use-cases is if a user prefers to be able to
> > recover stored information in case of a device failure (such recovery
> > will be impossible if SoC is damaged and HW-wrapped keys are used).
> 
> Isn't that already the case ? the BLK_CRYPTO_KEY_TYPE_HW_WRAPPED size is
> here to select HW-wrapped key, otherwise the ol' raw key is passed.
> Just look the next patch.
> 
> Or did I miss something ?

That's a good question. If use_hwkm is set, ICE gets programmed to use
hwkm (see qcom_ice_hwkm_init() call above). I'm not sure if it is
expected to work properly if after such a call we pass raw key.

> 
> Neil
> 
> > 
> > >   	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__ */
> > > 
> > > -- 
> > > 2.43.0
> > > 
> > 
> 

-- 
With best wishes
Dmitry