Messages in this thread |  | | Subject | Re: [PART2 PATCH v4 07/11] iommu/amd: Introduce amd_iommu_update_ga() | From | Suravee Suthikulpanit <> | Date | Thu, 14 Jul 2016 16:33:02 +0700 |
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On 7/14/16 16:13, Suravee Suthikulpanit wrote: >>> unsigned long flags; >>> + struct amd_iommu *iommu; >>> + >>> + if (!AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir)) >>> + return 0; >>> + >>> + for_each_iommu(iommu) { >>> + struct amd_ir_data *ir_data; >>> + >>> + spin_lock_irqsave(&iommu->gatag_ir_hash_lock, flags); >>> + >>> + /* Note: >>> + * We need to update all interrupt remapping table entries >>> + * for targeting the specified vcpu. Here, we use gatag >>> + * as a hash key and iterate through all entries in the bucket. >>> + */ >>> + hash_for_each_possible(iommu->gatag_ir_hash, ir_data, hnode, >>> + AMD_IOMMU_GATAG(vm_id, vcpu_id)) { >>> + struct irte_ga *irte = (struct irte_ga *) ir_data->entry; >> >> |>> (The ga_tag check is missing here too.) >> |> >> |> Here, the intention is to update all interrupt remapping entries in >> the >> |> bucket w/ the same GATAG (i.e. vm_id + vcpu_id), where GATAG = >> |> AMD_IOMMU_GATAG(vm_id, vcpu_id). >> >> Which is why you need to check that >> AMD_IOMMU_GATAG(vm_id, vcpu_id) == entry->fields_vapic.ga_tag >> >> The hashing function can map two different vm_id + vcpu_id to the same >> bucket and hash_for_each_possible() would return both of them, but only >> one belongs to the VCPU that we want to update. >> >> (And shouldn't there be only one match?) > > Actually, with your suggestion above, the hask key would be (vm_id & > 0x3FFFFF << 8)| (vcpu_id & 0xFF). So, it should be unique for each vcpu > of each vm, or am I still missing something?
Ok, one scenario would be when SVM run out of the VM_ID and having to start re-using them. Since we want SVM to generate ga_tag and just pass into IOMMU driver for it to program the IRTE, we probably can make an assumption that SVM would make sure that ga_tag would not conflict for each vm_id/vcpu_id.
Thanks, Suravee
Thanks, Suravee
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