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Re: [PATCH v8 09/13] arm/smmu-v3: add suspend/resume handlers
- To: Mykola Kvach <xakep.amatop@xxxxxxxxx>
- From: Luca Fancellu <Luca.Fancellu@xxxxxxx>
- Date: Fri, 8 May 2026 12:21:05 +0000
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Mykola Kvach <mykola_kvach@xxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Rahul Singh <Rahul.Singh@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Fri, 08 May 2026 12:22:34 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Nodisclaimer: true
- Thread-index: AQHc1k50BMsvUkAtf0yXvEOre8XAa7X/maIAgASD5YA=
- Thread-topic: [PATCH v8 09/13] arm/smmu-v3: add suspend/resume handlers
HI Mykola,
>>>
>>> -static int __init arm_smmu_device_reset(struct arm_smmu_device *smmu)
>>> +static int arm_smmu_device_reset(struct arm_smmu_device *smmu)
>>> {
>>> int ret;
>>> u32 reg, enables;
>>> @@ -2163,17 +2166,9 @@ static int __init arm_smmu_device_reset(struct
>>> arm_smmu_device *smmu)
>>> }
>>> }
>>>
>>> - ret = arm_smmu_setup_irqs(smmu);
>>> - if (ret) {
>>> - dev_err(smmu->dev, "failed to setup irqs\n");
>>
>> We are moving this one to the probe and ..
>>
>>> + ret = arm_smmu_enable_irqs(smmu);
>>> + if ( ret )
>>
>> changing with this one, but arm_smmu_setup_irqs() also calls
>> arm_smmu_setup_unique_irqs() which
>> calls arm_smmu_setup_msis(), are we sure that on resume we will get the same
>> state?
>
> This follows the split introduced in the Linux arm-smmu-v3 runtime/system
> sleep
> series:
>
> https://lore.kernel.org/linux-iommu/20260414194702.1229094-1-praan@xxxxxxxxxx/
>
> The intent is to keep IRQ handler registration as one-time probe state, while
> reset/resume only restores the SMMU hardware state and re-enables interrupt
> generation.
>
> You are right that the MSI case needs extra care. In the Linux series this is
> handled by arm_smmu_resume_msis(), which restores the SMMU-side MSI
> configuration. I did not port that part in this patch because Xen SMMUv3 MSI
> support is currently documented as unsupported and is not part of the
> supported/tested path, so this patch only covers the wired IRQ path used by
> Xen
> today.
>
> If Xen SMMUv3 MSI support becomes usable in the future, the resume path will
> need an equivalent MSI restore step before IRQ_CTRL is re-enabled.
In the mean time should we check maybe smmu->features doesn’t have
ARM_SMMU_FEAT_MSI flag and document it in commit message?
What do you think about it? I’m just worried someone uses CONFIG_MSI and your
feature and ends up in some trouble, while we know that your feature breaks
CONFIG_MSI.
Maybe the maintainers can give their opinion here as well.
Cheers,
Luca
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