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References: <20230112145424.3791276-1-etienne.carriere@linaro.org>
 <20230112145424.3791276-4-etienne.carriere@linaro.org> <86a62mokkq.wl-maz@kernel.org>
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From:   Etienne Carriere <etienne.carriere@linaro.org>
Date:   Fri, 13 Jan 2023 16:27:22 +0100
Message-ID: <CAN5uoS-Q5ePtNcJ2-8BBV+rxUK6xcbU1ywtcRfYf=sRbWShNpg@mail.gmail.com>
Subject: Re: [PATCH 3/3] optee core: add irq chip using optee async notification
To:     Marc Zyngier <maz@kernel.org>
Cc:     linux-kernel@vger.kernel.org,
        Jens Wiklander <jens.wiklander@linaro.org>,
        Sumit Garg <sumit.garg@linaro.org>,
        op-tee@lists.trustedfirmware.org, devicetree@vger.kernel.org,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Pascal Paillet <p.paillet@foss.st.com>,
        Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hello Marc,

Thanks for the review.


On Fri, 13 Jan 2023 at 10:22, Marc Zyngier <maz@kernel.org> wrote:
>
> On Thu, 12 Jan 2023 14:54:24 +0000,
> Etienne Carriere <etienne.carriere@linaro.org> wrote:
> >
> > Adds an irq chip in optee driver to generate interrupts from OP-TEE
> > notified interrupt events based on optee async notification. Upon such
> > notification, optee driver invokes OP-TEE to query a pending interrupt
> > event. If an interrupt notification is pending the invocation return
> > OPTEE_SMC_ASYNC_NOTIF_VALUE_DO_IT and optee driver can get the pending
> > interrupt number with SMC function ID OPTEE_SMC_FUNCID_GET_IT_VALUE.
> >
> > SMC function ID OPTEE_SMC_FUNCID_SET_IT_MASK allows Linux to mask/unmask
> > an interrupt notification services.
> >
> > The optee irq_chip if flagged IRQCHIP_SKIP_SET_WAKE to skip set_wake
> > as optee interrupt notifications doesn't support the set_wake option.
> > In case a device is using the optee irq and is marked as wakeup source,
> > this result in an "Unbalanced IRQ xx wake disable" backtrace, since:
> > - in irq_set_irq_wake(ON), wake_depth gets incremented, then reset due to
> >   set_irq_wake_real() returns an error (irq_set_wake() isn't implemented)
> > - in irq_set_irq_wake(OFF), wake_depth is always 0, hence the warning
>
> Is this relevant information?

The description is maybe too specific to the setup used for this feature.
I'll rephrase that, unless IRQCHIP_SKIP_SET_WAKE flag is not relevant here.

>
> >
> > Co-developed-by: Pascal Paillet <p.paillet@foss.st.com>
> > Signed-off-by: Pascal Paillet <p.paillet@foss.st.com>
> > Co-developed-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
> > Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
> > Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
> > ---
> >  drivers/tee/optee/optee_private.h |   2 +
> >  drivers/tee/optee/optee_smc.h     |  78 +++++++++++++++-
> >  drivers/tee/optee/smc_abi.c       | 142 ++++++++++++++++++++++++++++--
> >  3 files changed, 216 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/tee/optee/optee_private.h b/drivers/tee/optee/optee_private.h
> > index e5bd3548691f..2a146d884d27 100644
> > --- a/drivers/tee/optee/optee_private.h
> > +++ b/drivers/tee/optee/optee_private.h
> > @@ -112,6 +112,7 @@ struct optee_pcpu {
> >   * @optee_pcpu               per_cpu optee instance for per cpu work or NULL
> >   * @notif_pcpu_wq    workqueue for per cpu aynchronous notification or NULL
> >   * @notif_pcpu_work  work for per cpu asynchronous notification
> > + * @domain           interrupt domain registered by OP-TEE driver
> >   */
> >  struct optee_smc {
> >       optee_invoke_fn *invoke_fn;
> > @@ -121,6 +122,7 @@ struct optee_smc {
> >       struct optee_pcpu __percpu *optee_pcpu;
> >       struct workqueue_struct *notif_pcpu_wq;
> >       struct work_struct notif_pcpu_work;
> > +     struct irq_domain *domain;
> >  };
> >
> >  /**
> > diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.h
> > index 73b5e7760d10..0cf83d5a2931 100644
> > --- a/drivers/tee/optee/optee_smc.h
> > +++ b/drivers/tee/optee/optee_smc.h
> > @@ -226,7 +226,8 @@ struct optee_smc_get_shm_config_result {
> >   * a3        Bit[7:0]: Number of parameters needed for RPC to be supplied
> >   *             as the second MSG arg struct for
> >   *             OPTEE_SMC_CALL_WITH_ARG
> > - *   Bit[31:8]: Reserved (MBZ)
> > + *   Bit[23:8]: The maximum interrupt event notification number
> > + *   Bit[31:24]: Reserved (MBZ)
> >   * a4-7      Preserved
> >   *
> >   * Error return register usage:
> > @@ -254,6 +255,11 @@ struct optee_smc_get_shm_config_result {
> >  #define OPTEE_SMC_SEC_CAP_ASYNC_NOTIF                BIT(5)
> >  /* Secure world supports pre-allocating RPC arg struct */
> >  #define OPTEE_SMC_SEC_CAP_RPC_ARG            BIT(6)
> > +/* Secure world supports interrupt events notification to normal world */
> > +#define OPTEE_SMC_SEC_CAP_IT_NOTIF           BIT(7)
> > +
> > +#define OPTEE_SMC_SEC_CAP_MAX_NOTIF_IT_MASK  GENMASK(23, 8)
> > +#define OPTEE_SMC_SEC_CAP_MAX_NOTIF_IT_SHIFT 8
> >
> >  #define OPTEE_SMC_FUNCID_EXCHANGE_CAPABILITIES       9
> >  #define OPTEE_SMC_EXCHANGE_CAPABILITIES \
> > @@ -416,6 +422,12 @@ struct optee_smc_disable_shm_cache_result {
> >   */
> >  #define OPTEE_SMC_ASYNC_NOTIF_VALUE_DO_BOTTOM_HALF   0
> >
> > +/*
> > + * Notification that OP-TEE triggers an interrupt event to Linux kernel
> > + * for an interrupt consumer.
> > + */
> > +#define OPTEE_SMC_ASYNC_NOTIF_VALUE_DO_IT            1
> > +
> >  #define OPTEE_SMC_FUNCID_GET_ASYNC_NOTIF_VALUE       17
> >  #define OPTEE_SMC_GET_ASYNC_NOTIF_VALUE \
> >       OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_GET_ASYNC_NOTIF_VALUE)
> > @@ -426,6 +438,70 @@ struct optee_smc_disable_shm_cache_result {
> >  /* See OPTEE_SMC_CALL_WITH_REGD_ARG above */
> >  #define OPTEE_SMC_FUNCID_CALL_WITH_REGD_ARG  19
> >
> > +/*
> > + * Retrieve the interrupt number of the pending interrupt event notified to
> > + * non-secure world since the last call of this function.
> > + *
> > + * OP-TEE keeps a record of all posted interrupt notification events. When the
> > + * async notif interrupt is received by non-secure world, this function should
> > + * be called until all pended interrupt events have been retrieved. When an
> > + * interrupt event is retrieved it is cleared from the record in secure world.
> > + *
> > + * It is expected that this function is called from an interrupt handler
> > + * in normal world.
> > + *
> > + * Call requests usage:
> > + * a0        SMC Function ID, OPTEE_SMC_GET_IT_NOTIF_VALUE
> > + * a1-6      Not used
> > + * a7        Hypervisor Client ID register
> > + *
> > + * Normal return register usage:
> > + * a0        OPTEE_SMC_RETURN_OK
> > + * a1        IT_NOTIF interrupt identifier value
> > + * a2        Bit[0]: OPTEE_SMC_IT_NOTIF_VALID if the value in a1 is
> > + *           valid, else 0 if no interrupt event were pending
> > + * a2        Bit[1]: OPTEE_SMC_IT_NOTIF_PENDING if another interrupt event
> > + *           value is pending, else 0.
> > + *   Bit[31:2]: MBZ
> > + * a3-7      Preserved
> > + *
> > + * Not supported return register usage:
> > + * a0        OPTEE_SMC_RETURN_ENOTAVAIL
> > + * a1-7      Preserved
> > + */
> > +#define OPTEE_SMC_IT_NOTIF_VALID             BIT(0)
> > +#define OPTEE_SMC_IT_NOTIF_PENDING           BIT(1)
> > +
> > +#define OPTEE_SMC_FUNCID_GET_IT_NOTIF_VALUE  20
> > +#define OPTEE_SMC_GET_IT_NOTIF_VALUE \
> > +     OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_GET_IT_NOTIF_VALUE)
> > +
> > +/*
> > + * Mask or unmask an interrupt notification event.
> > + *
> > + * It is expected that this function is called from an interrupt handler
> > + * in normal world.
> > + *
> > + * Call requests usage:
> > + * a0        SMC Function ID, OPTEE_SMC_SET_IT_NOTIF_MASK
> > + * a1        Interrupt identifier value
> > + * a2        Bit[0]: 1 if interrupt event is to be masked, 0 if it is to be unmasked
> > + * a2   Bit[31:1] MBZ
> > + * a3-6      Not used
> > + * a7        Hypervisor Client ID register
> > + *
> > + * Normal return register usage:
> > + * a0        OPTEE_SMC_RETURN_OK
> > + * a1-7      Preserved
> > + *
> > + * Not supdealed ported return register usage:
> > + * a0        OPTEE_SMC_RETURN_ENOTAVAIL
> > + * a1-7      Preserved
> > + */
> > +#define OPTEE_SMC_FUNCID_SET_IT_NOTIF_MASK   21
> > +#define OPTEE_SMC_SET_IT_NOTIF_MASK \
> > +     OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_SET_IT_NOTIF_MASK)
> > +
> >  /*
> >   * Resume from RPC (for example after processing a foreign interrupt)
> >   *
> > diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c
> > index 8c2d58d605ac..0360afde119f 100644
> > --- a/drivers/tee/optee/smc_abi.c
> > +++ b/drivers/tee/optee/smc_abi.c
> > @@ -977,6 +977,112 @@ static int optee_smc_stop_async_notif(struct tee_context *ctx)
> >   * 5. Asynchronous notification
> >   */
> >
> > +static u32 get_it_value(optee_invoke_fn *invoke_fn, bool *value_valid,
> > +                     bool *value_pending)
>
> What value? If this is supposed to return a set of pending bits, just
> name the function to reflect that.

Communication between Linux kernel and OP-TEE is this case is rather
basic here, no shared memory used, only few CPU registers can be used
to shared information. So Linux invokes OP-TEE for each pending optee
interrupt event: each invocation returns a interrupt event number (an
integer value) and a status whether another interrupt event is pending
and shall be retrieved invoking OP-TEE again. In case Linux invoke
OP-TEE for a pending interrupt and none is pending, a last status is
also provided: 'value_valid'.

I could maybe change the prototype to something like:
static u32 get_pending_it_number(optee_invoke_fn *invoke_fn, bool
*it_number_valid, bool *more_pending_it)

>
> Also, at no point do you explain that each PPI is only a mux interrupt
> for a bunch of chained interrupts.

Sorry, I don't understand your question.
The "it notif" feature proposed in this change is not straight related a PPI.
Previous patch in this series is indeed related to PPI: it propose
optee driver can use a single PPI instead of a signle SPI for the
OP-TEE "asyn notification" feature.
This change allows to mux interrupts events (from OP-TEE to Linux
optee driver) over "OP-TEE async notif" means, which is using a single
SPI or PPI.
Maybe I should have submitted both changes separately :(

>
> > +{
> > +     struct arm_smccc_res res;
> > +
> > +     invoke_fn(OPTEE_SMC_GET_IT_NOTIF_VALUE, 0, 0, 0, 0, 0, 0, 0, &res);
> > +
> > +     if (res.a0)
> > +             return 0;
> > +
> > +     *value_valid = res.a2 & OPTEE_SMC_IT_NOTIF_VALID;
> > +     *value_pending = res.a2 & OPTEE_SMC_IT_NOTIF_PENDING;
> > +     return res.a1;
> > +}
> > +
> > +static u32 set_it_mask(optee_invoke_fn *invoke_fn, u32 it_value, bool mask)
> > +{
> > +     struct arm_smccc_res res;
> > +
> > +     invoke_fn(OPTEE_SMC_SET_IT_NOTIF_MASK, it_value, mask, 0, 0, 0, 0, 0, &res);
> > +
> > +     if (res.a0)
> > +             return 0;
> > +
> > +     return res.a1;
> > +}
> > +
> > +static int handle_optee_it(struct optee *optee)
> > +{
> > +     bool value_valid;
> > +     bool value_pending;
> > +     u32 it;
> > +
> > +     do {
> > +             struct irq_desc *desc;
> > +
> > +             it = get_it_value(optee->smc.invoke_fn, &value_valid, &value_pending);
> > +             if (!value_valid)
> > +                     break;
> > +
> > +             desc = irq_to_desc(irq_find_mapping(optee->smc.domain, it));
> > +             if (!desc) {
> > +                     pr_err("no desc for optee IT:%d\n", it);
> > +                     return -EIO;
> > +             }
> > +
> > +             handle_simple_irq(desc);
> > +
>
> What is this? Please use generic_handle_domain_irq(), like any other
> driver. Why is the flow handler handle_simple_irq()? You need to
> explain what the signalling is for the secure-provided interrupts.

My fault. I thought handle_simple_irq() would better apply here since
its description:
 * Simple interrupts are either sent from a demultiplexing interrupt
 * handler or come from hardware, where no interrupt hardware control
 * is necessary.

OP-TEE secure world has already dealt with the HW interrupt resources
(ack/etc...) before it notifies Linux kernel of the event.

>
> > +     } while (value_pending);
> > +
> > +     return 0;
> > +}
> > +
> > +static void optee_it_irq_mask(struct irq_data *d)
> > +{
> > +     struct optee *optee = d->domain->host_data;
> > +
> > +     set_it_mask(optee->smc.invoke_fn, d->hwirq, true);
> > +}
> > +
> > +static void optee_it_irq_unmask(struct irq_data *d)
> > +{
> > +     struct optee *optee = d->domain->host_data;
> > +
> > +     set_it_mask(optee->smc.invoke_fn, d->hwirq, false);
> > +}
> > +
> > +static struct irq_chip optee_it_irq_chip = {
> > +     .name = "optee-it",
> > +     .irq_disable = optee_it_irq_mask,
> > +     .irq_enable = optee_it_irq_unmask,
> > +     .flags = IRQCHIP_SKIP_SET_WAKE,
>
> Is it a mask or a disable? These are different beasts.

Indeed, thanks for catching that. I think we need to 4
(enable/disable/mask/unmask).
I'll fix.

>
> > +};
> > +
> > +static int optee_it_alloc(struct irq_domain *d, unsigned int virq,
> > +                       unsigned int nr_irqs, void *data)
> > +{
> > +     struct irq_fwspec *fwspec = data;
> > +     irq_hw_number_t hwirq;
> > +
> > +     hwirq = fwspec->param[0];
> > +
> > +     irq_domain_set_hwirq_and_chip(d, virq, hwirq, &optee_it_irq_chip, d->host_data);
> > +
> > +     return 0;
> > +}
> > +
> > +static const struct irq_domain_ops optee_it_irq_domain_ops = {
> > +     .alloc = optee_it_alloc,
> > +     .free = irq_domain_free_irqs_common,
> > +};
> > +
> > +static int optee_irq_domain_init(struct platform_device *pdev, struct optee *optee, u_int max_it)
> > +{
> > +     struct device *dev = &pdev->dev;
> > +     struct device_node *np = dev->of_node;
> > +
> > +     optee->smc.domain = irq_domain_add_linear(np, max_it, &optee_it_irq_domain_ops, optee);
> > +     if (!optee->smc.domain) {
> > +             dev_err(dev, "Unable to add irq domain\n");
> > +             return -ENOMEM;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> >  static u32 get_async_notif_value(optee_invoke_fn *invoke_fn, bool *value_valid,
> >                                bool *value_pending)
> >  {
> > @@ -1008,13 +1114,15 @@ static irqreturn_t notif_irq_handler(int irq, void *dev_id)
> >       }
> >
> >       do {
> > -             value = get_async_notif_value(optee->smc.invoke_fn,
> > -                                           &value_valid, &value_pending);
> > +             value = get_async_notif_value(optee->smc.invoke_fn, &value_valid, &value_pending);
> >               if (!value_valid)
> >                       break;
> >
> >               if (value == OPTEE_SMC_ASYNC_NOTIF_VALUE_DO_BOTTOM_HALF)
> >                       do_bottom_half = true;
> > +             else if (optee->smc.sec_caps & OPTEE_SMC_SEC_CAP_IT_NOTIF &&
> > +                      value == OPTEE_SMC_ASYNC_NOTIF_VALUE_DO_IT)
> > +                     handle_optee_it(optee);
>
> NAK. This isn't how we deal with chained interrupts. Definitely not in
> an interrupt handler.

My apologies, what is wrong in this sequence. My expectations are:
1- Something happens on OP-TEE secure side that should be reported to
Linux as a software interrupt event
2- OP-TEE (secure world) raises an HW interrupt to notify Linux optee
driver that event(s) are pending
3- optee driver threade_irq handler is called and asks OP-TEE which
are the pending events. This is done event per event until all pending
event are consumed.
4- Each each pending events:
4a- (existing code) wake or spawn a thread when a pending event is
related to a threaded context execution,
4b- (this patch) call the interrupt handler of the optee interrupt
consumers when event is related to an interrupt event signalling,

Regards,
Etienne

>
>         M.
>
> --
> Without deviation from the norm, progress is not possible.