Messages in this thread | | | Date | Wed, 15 Jun 2022 21:10:19 +0800 | Subject | Re: [PATCH v2 03/12] iommu/vt-d: Remove clearing translation data in disable_dmar_iommu() | From | Baolu Lu <> |
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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); } }
Best regards, baolu
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