Messages in this thread | | | Date | Tue, 28 Nov 2023 22:59:33 +0000 | Subject | Re: [PATCH 06/16] iommu/dma: use page allocation function provided by iommu-pages.h | From | Robin Murphy <> |
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On 2023-11-28 10:50 pm, Pasha Tatashin wrote: > On Tue, Nov 28, 2023 at 5:34 PM Robin Murphy <robin.murphy@arm.com> wrote: >> >> On 2023-11-28 8:49 pm, Pasha Tatashin wrote: >>> Convert iommu/dma-iommu.c to use the new page allocation functions >>> provided in iommu-pages.h. >> >> These have nothing to do with IOMMU pagetables, they are DMA buffers and >> they belong to whoever called the corresponding dma_alloc_* function. > > Hi Robin, > > 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.
Thanks, Robin.
> Since, I included DMA memory, I specifically removed mentioning of > IOMMU page tables in the most of places, and only report it as IOMMU > memory. However, since it is still bundled together with SecPageTables > it can be confusing. > > Pasha
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