Re: [PATCH v2 03/12] iommu/vt-d: Remove clearing translation data in disable_dmar_iommu()

[Baolu Lu]

On 2022/6/14 14:49, Tian, Kevin wrote:
> > From: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
> > 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