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SubjectRe: [PATCH v2 03/12] iommu/vt-d: Remove clearing translation data in disable_dmar_iommu()
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On 2022/6/14 14:49, Tian, Kevin wrote:
>> From: Lu Baolu<baolu.lu@linux.intel.com>
>> Sent: Tuesday, June 14, 2022 10:51 AM
>>
>> The disable_dmar_iommu() is called when IOMMU initialization fails or
>> the IOMMU is hot-removed from the system. In both cases, there is no
>> need to clear the IOMMU translation data structures for devices.
>>
>> On the initialization path, the device probing only happens after the
>> IOMMU is initialized successfully, hence there're no translation data
>> structures.
> Out of curiosity. With kexec the IOMMU may contain stale mappings
> from the old kernel. Then is it meaningful to disable IOMMU after the
> new kernel fails to initialize it properly?

For kexec kernel, if the IOMMU is detected to be pre-enabled, the IOMMU
driver will try to copy tables from the old kernel. If copying table
fails, the IOMMU driver will disable IOMMU and do the normal
initialization.

Best regards,
baolu

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