Re: [PATCH 06/16] iommu/dma: use page allocation function provided by iommu-pages.h
From: Pasha Tatashin <pasha.tatashin@soleen.com>
Date: 2023-11-28 23:08:49
Also in:
asahi, cgroups, kvm, linux-doc, linux-fsdevel, linux-iommu, linux-mm, linux-rockchip, linux-samsung-soc, linux-sunxi, linux-tegra, lkml, virtualization
quoted
This is true, however, we want to account and observe the pages allocated by IOMMU subsystem for DMA buffers, as they are essentially unmovable locked pages. Should we separate IOMMU memory from KVM memory all together and add another field to /proc/meminfo, something like "iommu -> iommu pagetable and dma memory", or do we want to export DMA memory separately from IOMMU page tables?These are not allocated by "the IOMMU subsystem", they are allocated by the DMA API. Even if you want to claim that a driver pinning memory via iommu_dma_ops is somehow different from the same driver pinning the same amount of memory via dma-direct when iommu.passthrough=1, it's still nonsense because you're failing to account the pages which iommu_dma_ops gets from CMA, dma_common_alloc_pages(), dynamic SWIOTLB, the various pools, and so on.
I see, IOMMU variants are used only for discontiguous allocations, and the common ones are defined outside of driver/iommu. Alright, I can remove all the changes for all no-page table related IOMMU allocations. Pasha