Messages in this thread | | | From | "Tian, Kevin" <> | Subject | RE: [PATCH v2 03/12] iommu/vt-d: Remove clearing translation data in disable_dmar_iommu() | Date | Thu, 16 Jun 2022 04:00:40 +0000 |
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> From: Baolu Lu <baolu.lu@linux.intel.com> > Sent: Wednesday, June 15, 2022 9:10 PM > > On 2022/6/15 14:22, Tian, Kevin wrote: > >> From: Baolu Lu <baolu.lu@linux.intel.com> > >> Sent: Tuesday, June 14, 2022 3:21 PM > >> > >> 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. > >> > > > > What about an error occurred after copying table in the initialization > > path? The new kernel will be in a state assuming iommu is disabled > > but it is still enabled using an old mapping for certain devices... > > > > If copying table failed, the translation will be disabled and a clean > root table will be used. > > if (translation_pre_enabled(iommu)) { > pr_info("Translation already enabled - trying to copy > translation structures\n"); > > ret = copy_translation_tables(iommu); > if (ret) { > /* > * We found the IOMMU with translation > * enabled - but failed to copy over the > * old root-entry table. Try to proceed > * by disabling translation now and > * allocating a clean root-entry table. > * This might cause DMAR faults, but > * probably the dump will still succeed. > */ > pr_err("Failed to copy translation tables from previous > kernel for %s\n", > iommu->name); > iommu_disable_translation(iommu); > clear_translation_pre_enabled(iommu); > } else { > pr_info("Copied translation tables from previous kernel > for %s\n", > iommu->name); > } > } >
I meant copying table succeeds but another error occurs in the remaining path of initialization...
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