Messages in this thread | | | Date | Mon, 29 Aug 2022 17:28:40 +0800 | Subject | Re: [PATCH 1/2] genirq: Record dangling hwirq number into struct irq_data | From | "liaochang (A)" <> |
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在 2022/8/28 0:15, Marc Zyngier 写道: > On Thu, 25 Aug 2022 07:08:18 +0100, > Liao Chang <liaochang1@huawei.com> wrote: >> >> Following interrupt allocation process lead to some interrupts are >> mapped in the low-level domain(Arm ITS), but they are never been mapped >> at the higher level. >> >> irq_domain_alloc_irqs_hierarchy(.., nr_irqs, ...) >> its_irq_domain_alloc(..., nr_irqs, ...) >> its_alloc_device_irq(..., nr_irqs, ...) >> bitmap_find_free_region(..., get_count_order(nr_irqs)) >> >> Since ITS domain find a region of zero bits, the length of which must >> aligned to power of two. If nr_irqs is 30, the length of zero bits is >> actually 32, but only first 30 bits are really mapped. >> >> On teardown, low-level domain only free these interrupts that actually >> mapped, and leave last interrupts dangling in the ITS domain. Thus the >> ITS device resources are never freed. On device driver reload, dangling >> interrupts prevent ITS domain from allocating enough resource. >> >> irq_domain_free_irqs_hierarchy(..., nr_irqs, ...) >> its_irq_domain_free(..., irq_base + i, 1) >> bitmap_release_region(..., irq_base + i, get_count_order(1)) >> >> John reported this problem to LKML and Marc provided a solution and fix >> it in the generic code, see the discussion from Link tag. Marc's patch >> fix John's problem, but does not take care of some corner case, look one >> example below. >> >> Step1: 32 interrupts allocated in LPI domain, but return the first 30 to >> higher driver. >> >> 111111111111111111111111111111 11 >> |<------------0~29------------>|30,31| >> >> Step2: interrupt #16~28 are released one by one, then #0~15 and #29~31 >> still be there. >> >> 1111111111111111 0000000000000 1 11 >> |<-----0~15----->|<---16~28--->|29|30,31| >> >> Step#: on driver teardown, generic code will invoke ITS domain code >> twice. The first time, #0~15 will be released, the second one, only #29 >> will be released(1 align to power of two). >> >> 0000000000000000 0000000000000 0 11 >> |<-----0~15----->|<---16~28--->|29|30,31| >> >> In short summary, the dangling problem stems from the number of released >> hwirq is less than the one of allocated hwirq in ITS domain. In order to >> fix this problem, make irq_data record the number of allocated but >> unmapped hwirq. If hwirq followed by some unmapped bits, ITS domain >> record the number of unmapped bits to the last irq_data mapped to higher >> level, when the last hwirq followed by unmapped hwirq is released, some >> dangling bit will be clear eventualy, look back the trivial example >> above. >> >> Step1: record '2' into the irq_data.dangling of #29 hwirq. >> >> 111111111111111111111111111111 11 >> |<------------0~29------------>|30,31| >> dangling: 000000000000000000000000000002 >> >> Step2: no change >> >> 1111111111111111 0000000000000 1 11 >> |<-----0~15----->|<---16~28--->|29|30,31| >> dangling: 0000000000000000 0000000000000 2 >> >> Step3: ITS domain will release #30~31 since the irq_data.dangling of #29 >> is '2'. >> >> 0000000000000000 0000000000000 0 00 >> |<-----0~15----->|<---16~28--->|29|30,31| >> dangling: 0000000000000000 0000000000000 2 >> >> Fixes: 4615fbc3788dd ("genirq/irqdomain: Don't try to free an interrupt >> that has no mapping") >> Reported-by: John Garry <john.garry@huawei.com> >> Signed-off-by: Liao Chang <liaochang1@huawei.com> >> Link: https://lore.kernel.org/lkml/3d3d0155e66429968cb4f6b4feeae4b3@kernel.org/ >> --- >> include/linux/irq.h | 10 ++++++++++ >> 1 file changed, 10 insertions(+) >> >> diff --git a/include/linux/irq.h b/include/linux/irq.h >> index c3eb89606c2b..c48f10a0c230 100644 >> --- a/include/linux/irq.h >> +++ b/include/linux/irq.h >> @@ -167,6 +167,10 @@ struct irq_common_data { >> * @mask: precomputed bitmask for accessing the chip registers >> * @irq: interrupt number >> * @hwirq: hardware interrupt number, local to the interrupt domain >> + * @dangling: amount of dangling hardware interrupt, Arm ITS allocate >> + * hardware interrupt more than expected, aligned to power >> + * of two, so that unsued interrupt number become dangling. >> + * Use this field to record dangling bits follwoing @hwirq. >> * @common: point to data shared by all irqchips >> * @chip: low level interrupt hardware access >> * @domain: Interrupt translation domain; responsible for mapping >> @@ -180,6 +184,7 @@ struct irq_data { >> u32 mask; >> unsigned int irq; >> unsigned long hwirq; >> + unsigned long dangling; >> struct irq_common_data *common; >> struct irq_chip *chip; >> struct irq_domain *domain; > > > There is no way I will put ITS-specific hacks in the core, and I > really don't think this is the correct way to address this. Also, why > track this sort of thing on a per-interrupt basis, while this is > obviously a device-level allocation? Thanks for comment, my older version is introduce a dangling bitmap in ITS irq_domain at the cose of one more bitmap. such as like this:
struct event_lpi_map { unsigned long *lpi_map; + unsigned long *dangling_map; ... }
+dev->event.map.dangling_map = bitmap_alloc(nevc);
Obviously this dangling bitmap is likely to be sparse, which means most of bits are wasted, hence I decide to record dangling bits into the per-interrupt object. Well, it sounds a bad idea... > > The real issue is that there is currently no way for the ITS code to > know when we're done with *all* the interrupts of a device. This is > what needs fixing.
Let my understand what you mean, you are saying let **device driver** record these mapped and dangling interrupts, and free these dangling interrupts explicitly when driver is uninstall.
> > M. >
-- BR, Liao, Chang
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