On Tue, Oct 27, 2015 at 09:47:48AM +0900, Jerome Glisse wrote: > 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.gli...@gmail.com wrote: > > > From: Jérôme Glisse <jgli...@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 :)
Ok my bad amd actualy is using IOMMU_INIT_FINISH() so it finish before trying other. Which make sense for AMD as AMD driver will call the gart init gart_iommu_init() if it fails to initialize. If we ever end up with a platform with multiple IOMMU beside AMD then we need to switch to the IOMMU_INIT() instead of the finish one. Cheers, Jérôme -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
