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SubjectRe: [PATCH 03/35] irqchip/gic-v3-its: Allow LPI invalidation via the DirectLPI interface
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Hi Zenghui,

On 26/09/2019 15:57, Zenghui Yu wrote:
> Hi Marc,
>
> I get one kernel panic with this patch on D05.

Ah, surprise! I haven't had time to test this on a D05 yet, such in a
hurry to push the damn thing out of the building...

>
> (I don't have the GICv4.1 board at the moment. I have to wait for the
> appropriate HW to do more tests.)
>
> On 2019/9/24 2:25, Marc Zyngier wrote:
>> We currently don't make much use of the DirectLPI feature, and it would
>> be beneficial to do this more, if only because it becomes a mandatory
>> feature for GICv4.1.
>>
>> Signed-off-by: Marc Zyngier <maz@kernel.org>
>> ---
>> drivers/irqchip/irq-gic-v3-its.c | 51 +++++++++++++++++++++++---------
>> 1 file changed, 37 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
>> index 58cb233cf138..c94eb287393b 100644
>> --- a/drivers/irqchip/irq-gic-v3-its.c
>> +++ b/drivers/irqchip/irq-gic-v3-its.c
>> @@ -175,6 +175,12 @@ static DEFINE_IDA(its_vpeid_ida);
>> #define gic_data_rdist_rd_base() (gic_data_rdist()->rd_base)
>> #define gic_data_rdist_vlpi_base() (gic_data_rdist_rd_base() + SZ_128K)
>>
>> +static inline u32 its_get_event_id(struct irq_data *d)
>> +{
>> + struct its_device *its_dev = irq_data_get_irq_chip_data(d);
>> + return d->hwirq - its_dev->event_map.lpi_base;
>> +}
>> +
>> static struct its_collection *dev_event_to_col(struct its_device *its_dev,
>> u32 event)
>> {
>> @@ -183,6 +189,13 @@ static struct its_collection *dev_event_to_col(struct its_device *its_dev,
>> return its->collections + its_dev->event_map.col_map[event];
>> }
>>
>> +static struct its_collection *irq_to_col(struct irq_data *d)
>> +{
>> + struct its_device *its_dev = irq_data_get_irq_chip_data(d);
>> +
>> + return dev_event_to_col(its_dev, its_get_event_id(d));
>> +}
>> +
>
> irq_to_col uses device's event_map and col_map to get the target
> collection, yes it works well with device's LPI.
> But direct_lpi_inv also pass doorbells to it...
>
> We don't allocate doorbells for any devices, instead for each vPE.

Hmm. Yes, you're right. It looks like I've been carried away on this
one. I'll have a look.

>
> And see below,
>
>> static struct its_collection *valid_col(struct its_collection *col)
>> {
>> if (WARN_ON_ONCE(col->target_address & GENMASK_ULL(15, 0)))
>> @@ -1031,12 +1044,6 @@ static void its_send_vinvall(struct its_node *its, struct its_vpe *vpe)
>> * irqchip functions - assumes MSI, mostly.
>> */
>>
>> -static inline u32 its_get_event_id(struct irq_data *d)
>> -{
>> - struct its_device *its_dev = irq_data_get_irq_chip_data(d);
>> - return d->hwirq - its_dev->event_map.lpi_base;
>> -}
>> -
>> static void lpi_write_config(struct irq_data *d, u8 clr, u8 set)
>> {
>> irq_hw_number_t hwirq;
>> @@ -1081,12 +1088,28 @@ static void wait_for_syncr(void __iomem *rdbase)
>> cpu_relax();
>> }
>>
>> +static void direct_lpi_inv(struct irq_data *d)
>> +{
>> + struct its_collection *col;
>> + void __iomem *rdbase;
>> +
>> + /* Target the redistributor this LPI is currently routed to */
>> + col = irq_to_col(d);
>> + rdbase = per_cpu_ptr(gic_rdists->rdist, col->col_id)->rd_base;
>> + gic_write_lpir(d->hwirq, rdbase + GICR_INVLPIR);
>> +
>> + wait_for_syncr(rdbase);
>> +}
>> +
>> static void lpi_update_config(struct irq_data *d, u8 clr, u8 set)
>> {
>> struct its_device *its_dev = irq_data_get_irq_chip_data(d);
>>
>> lpi_write_config(d, clr, set);
>> - its_send_inv(its_dev, its_get_event_id(d));
>> + if (gic_rdists->has_direct_lpi && !irqd_is_forwarded_to_vcpu(d))
>> + direct_lpi_inv(d);
>> + else
>> + its_send_inv(its_dev, its_get_event_id(d));
>> }
>>
>> static void its_vlpi_set_doorbell(struct irq_data *d, bool enable)
>> @@ -2912,15 +2935,15 @@ static void its_vpe_send_cmd(struct its_vpe *vpe,
>>
>> static void its_vpe_send_inv(struct irq_data *d)
>> {
>> - struct its_vpe *vpe = irq_data_get_irq_chip_data(d);
>> -
>> if (gic_rdists->has_direct_lpi) {
>> - void __iomem *rdbase;
>> -
>> - rdbase = per_cpu_ptr(gic_rdists->rdist, vpe->col_idx)->rd_base;
>> - gic_write_lpir(vpe->vpe_db_lpi, rdbase + GICR_INVLPIR);
>> - wait_for_syncr(rdbase);
>> + /*
>> + * Don't mess about. Generating the invalidation is easily
>> + * done by using the parent irq_data, just like below.
>> + */
>> + direct_lpi_inv(d->parent_data);
>
> "GICv4-vpe"'s parent is "GICv3", not "ITS". What do we expect with
> irq_data_get_irq_chip_data(parent's irq_data)?

Yup, terrible mix up. d->parent_data comes from the fact that we want to
invalidate the LPI and not d->hwirq (which is the VPEID). But doing so,
we also confuse direct_lpi_inv(), which expects to find meaningful data
(the its_dev) as chip data (and the irq_to_col doesn't help either).

To sum it up, the whole thing is busted, I'll have a brown paper bag,
thank you very much... :-(. Let me work on a fix.

Thanks,

M.
--
Jazz is not dead, it just smells funny...

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