> Subject: RE: Support SVM without PASID > > > From: valmiki [mailto:valmikibow@xxxxxxxxx] > > Sent: Saturday, August 12, 2017 8:11 PM > > > > On 8/7/2017 4:01 PM, Jean-Philippe Brucker wrote: > > > On 05/08/17 06:14, valmiki wrote: > > > [...] > > >> Hi Jean, Thanks a lot, now i understood the flow. From vfio kernel > > >> documentation we fill vaddr and iova in struct > > vfio_iommu_type1_dma_map > > >> and pass them to VFIO. But if we use dynamic allocation in > > >> application (say malloc), do we need to use dma API to get iova and > > >> then call VFIO_IOMMU_MAP ioctl ? > > >> If application needs multiple such dynamic allocations, then it > > >> need to allocate large chunk and program it via VFIO_IOMMU_MAP > > >> ioctl and > > then > > >> manage rest allocations requirements from this buffer ? > > > > > > Yes, without SVM, the application allocates large buffers, allocates > > > IOVAs itself, and maps them with VFIO_IOMMU_MAP. Userspace doesn't > > > rely > > on the > > > DMA API at all, it manages IOVAs as it wants. Sizes passed to > > > VFIO_IOMMU_MAP have to be multiples of the MMU or IOMMU page > > granularity > > > (that is at least 4kB), and both iova and vaddr have to be aligned > > > on that granularity as well. So malloc isn't really suitable in this > > > case, you'll need mmap. The application can then implement a small > > > allocator to > > manage > > > the DMA pool created with VFIO_IOMMU_MAP. > > > > Thanks Jean, I have a confusion allocate IOVA's in userspace means, > > how can user application decide IOVA address, can user application > > pick any random IOVA address ? > > > > yes, any address. In this mode the whole IOVA address space is owned by > application, which just needs to use VFIO_IOMMU_MAP to setup > IOVA->PA mapping in IOMMU (As Jean pointed out, input paramters > are iova and vaddr. VFIO will figure out pa corresponding to vaddr). > Hi Kevin, I have a doubt in this case, what if someone assigns mmap returned virtual address as iova address, then EP will assume it is generating request on IOVA but in reality we are using application allocated virtual address, then it looks like we are working with application virtual address directly without PASID. Is this valid ? Regards, Bharat
