> From: Jason Wang [mailto:jasowang@xxxxxxxxxx] > Sent: Thursday, October 31, 2019 5:33 AM > Subject: Re: [RFC v2 00/22] intel_iommu: expose Shared Virtual Addressing to VM > > > On 2019/10/25 下午6:12, Tian, Kevin wrote: > >> From: Jason Wang [mailto:jasowang@xxxxxxxxxx] > >> Sent: Friday, October 25, 2019 5:49 PM > >> > >> > >> On 2019/10/24 下午8:34, Liu Yi L wrote: > >>> Shared virtual address (SVA), a.k.a, Shared virtual memory (SVM) on > >>> Intel platforms allow address space sharing between device DMA and > >> applications. > >> > >> > >> Interesting, so the below figure demonstrates the case of VM. I > >> wonder how much differences if we compare it with doing SVM between > >> device and an ordinary process (e.g dpdk)? > >> > >> Thanks > > One difference is that ordinary process requires only stage-1 > > translation, while VM requires nested translation. > > > A silly question, then I believe there's no need for VFIO DMA API in this case consider > the page table is shared between MMU and IOMMU? Echo Kevin's reply. We use nested translation here. For stage-1, yes, no need to use VFIO DMA API. For stage-2, we still use VFIO DMA API to program the GPA->HPA mapping to host. :-) Regards, Yi Liu > > Thanks > > >
