Messages in this thread | | | Date | Tue, 27 Oct 2015 09:47:48 +0900 | From | Jerome Glisse <> | Subject | Re: [PATCH] iommu/amd: Fix amd_iommu_detect() (does not fix any issues). |
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On Mon, Oct 26, 2015 at 12:07:17PM -0400, Konrad Rzeszutek Wilk wrote: > On Mon, Aug 31, 2015 at 06:13:03PM -0400, j.glisse@gmail.com wrote: > > From: Jérôme Glisse <jglisse@redhat.com> > > > > Fix amd_iommu_detect() to return positive value on success, like > > intended, and not zero. This will not change anything in the end > > as AMD IOMMU disable swiotlb and properly associate itself with > > Not sure how it disables SWIOTLB? The AMD Vi does not seem to > change 'swiotlb'. While 'gart_iommu_init' does. Did you mean > the AMD GART code?
So this is convoluted and painfull, each i look back at that it takes me time to figure out of thing happen. Basicly amd_iommu_init_dma_ops() will replace dma_ops to no_mmu unless passthrough, and when the AMD iommu associate itself with each device it will set the archdata.dma_ops again this unbind the default of swiotlb that is initialize before hw IOMMU.
> > > devices even if detect() doesn't return a positive value. > > Returning positive will mean that the pci_iommu_alloc will stop > processing _all_ other IOMMUs. > > While returning 0 will let it detect the other IOMMUs.
No see the IOMMU_FINISH_IF_DETECTED flags in pci_iommu_alloc(). Which is not set for AMD hence my patch should not change anything it (AFAICT and from testing but i do not have all AMD hw the ever existed).
So i am just making the detect function do what the API doc says it should do. See line 72 to 80 of : arch/x86/include/asm/iommu_table.h
> > Granted on an AMD machine there can be two 'IOMMU's - the GART > and the AMD Vi. The detection is always to call gart_iommu_hole_init > first, then amd_iommu_detect. > > I presume if there was one more type on AMD we would run into trouble.
No because of IOMMU_FINISH_IF_DETECTED flag.
Hope this clarify thing this spagethi mix :)
Cheers, Jérôme
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