Messages in this thread | | | Subject | Re: [RFC v1 5/8] mshv: add paravirtualized IOMMU support | From | Praveen Kumar <> | Date | Wed, 4 Aug 2021 12:13:42 +0530 |
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On 04-08-2021 03:17, Wei Liu wrote: >>> +static size_t hv_iommu_unmap(struct iommu_domain *d, unsigned long iova, >>> + size_t size, struct iommu_iotlb_gather *gather) >>> +{ >>> + size_t unmapped; >>> + struct hv_iommu_domain *domain = to_hv_iommu_domain(d); >>> + unsigned long flags, npages; >>> + struct hv_input_unmap_device_gpa_pages *input; >>> + u64 status; >>> + >>> + unmapped = hv_iommu_del_mappings(domain, iova, size); >>> + if (unmapped < size) >>> + return 0; >> Is there a case where unmapped > 0 && unmapped < size ? >> > There could be such a case -- hv_iommu_del_mappings' return value is >= 0. > Is there a problem with this predicate?
What I understand, if we are unmapping and return 0, means nothing was unmapped, and will that not cause any corruption or illegal access of unmapped memory later? From __iommu_unmap ... 13 while (unmapped < size) { 12 size_t pgsize = iommu_pgsize(domain, iova, size - unmapped); 11 10 unmapped_page = ops->unmap(domain, iova, pgsize, iotlb_gather); 9 if (!unmapped_page) 8 break; <<< we just break here, thinking there is nothing unmapped, but actually hv_iommu_del_mappings has removed some pages. 7 6 pr_debug("unmapped: iova 0x%lx size 0x%zx\n", 5 ¦iova, unmapped_page); 4 3 iova += unmapped_page; 2 unmapped += unmapped_page; 1 } ...
Am I missing something ?
Regards,
~Praveen.
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