Hi Tony, On Thu, 13 May 2021 12:57:49 -0700, "Luck, Tony" <[email protected]> wrote:
> On Thu, May 13, 2021 at 12:46:21PM -0700, Jacob Pan wrote: > > It seems there are two options: > > 1. Add a new IOMMU API to set up a system PASID with a *separate* IOMMU > > page table/domain, mark the device is PASID only with a flag. Use DMA > > APIs to explicit map/unmap. Based on this PASID-only flag, Vendor IOMMU > > driver will decide whether to use system PASID domain during map/unmap. > > Not clear if we also need to make IOVA==kernel VA. > > > > 2. Add a new IOMMU API to setup a system PASID which points to > > init_mm.pgd. This API only allows trusted device to bind with the > > system PASID at its own risk. There is no need for DMA API. This is the > > same as the current code except with an explicit API. > > > > Which option? > > Option #1 looks cleaner to me. Option #2 gives access to bits > of memory that the users of system PASID shouldn't ever need > to touch ... just map regions of memory that the kernel has > a "struct page" for. > > What does "use DMA APIs to explicitly map/unmap" mean? Is that > for the whole region? > If we map the entire kernel direct map during system PASID setup, then we don't need to use DMA API to map/unmap certain range. I was thinking this system PASID page table could be on-demand. The mapping is built by explicit use of DMA map/unmap APIs. > I'm expecting that once this system PASID has been initialized, > then any accelerator device with a kernel use case would use the > same PASID. I.e. DSA for page clearing, IAX for ZSwap compression > & decompression, etc. > OK, sounds like we have to map the entire kernel VA with struct page as you said. So we still by-pass DMA APIs, can we all agree on that? > -Tony Thanks, Jacob _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
