Messages in this thread | | | Date | Thu, 8 Sep 2022 14:13:19 +0800 | From | Baolu Lu <> | Subject | Re: [PATCH 1/1] iommu/vt-d: Fix possible recursive locking in intel_iommu_init() |
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Hi Kevin,
On 2022/7/25 17:39, Baolu Lu wrote: > On 2022/7/25 15:40, Tian, Kevin wrote: >>> From: Baolu Lu <baolu.lu@linux.intel.com> >>> Sent: Sunday, July 24, 2022 11:00 AM >>> >>> Hi Kevin, >>> >>> On 2022/7/21 15:39, Tian, Kevin wrote: >>>>> From: Lu Baolu <baolu.lu@linux.intel.com> >>>>> Sent: Tuesday, July 19, 2022 7:53 AM >>>>> >>>>> @@ -88,7 +89,8 @@ extern struct list_head dmar_drhd_units; >>>>> static inline bool dmar_rcu_check(void) >>>>> { >>>>> return rwsem_is_locked(&dmar_global_lock) || >>>>> - system_state == SYSTEM_BOOTING; >>>>> + system_state == SYSTEM_BOOTING || >>>>> + (IS_ENABLED(CONFIG_INTEL_IOMMU) >>>>> && !intel_iommu_enabled); >>>>> } >>>> >>>> intel_iommu_enabled is 0 if CONFIG_INTEL_IOMMU is not set. >>>> >>>> same for other similar checks. >>> >>> Sorry that I didn't get your point. If CONFIG_INTEL_IOMMU is not set, >>> IS_ENABLED(CONFIG_INTEL_IOMMU) is 0. The adding check has no effect. >>> Did >>> I miss anything? >>> >> >> My point was that the check on CONFIG_INTEL_IOMMU is unnecessary. > > Oh, if INTEL_IOMMU is not configured, the interrupt remapping could also > be supported, so we still need the rcu protection. We only relax the rcu > check when INTEL_IOMMU is configured, but not enabled yet.
The next stepping, we will tie INTEL_IOMMU and VT-d IRQ_REMAPPING together, that will make the VT-d software simpler.
Joerg also proposed this in another discussion thread:
https://lore.kernel.org/all/YrVPelnOi9nql%2F8C@8bytes.org/
After that, we have no need to add above check anymore. As this is a quick fix for lockdep splat, we don't need to wait until that done.
Does this work for you?
Best regards, baolu
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