On Mon, Feb 11, 2019 at 09:41:19AM -0800, Dave Hansen wrote: > On 2/9/19 4:44 PM, Michael S. Tsirkin wrote: > > So the policy should not leak into host/guest interface. > > Instead it is better to just keep the pages pinned and > > ignore the hint for now. > > It does seems a bit silly to have guests forever hinting about freed > memory when the host never has a hope of doing anything about it. > > Is that part fixable? Yes just not with existing IOMMU APIs. It's in the paragraph just above that you cut out: Yes right now assignment is not smart enough but generally you can protect the unused page in the IOMMU and that's it, it's safe. So e.g. extern int iommu_remap(struct iommu_domain *domain, unsigned long iova, phys_addr_t paddr, size_t size, int prot); I can elaborate if you like but generally we would need an API that allows you to atomically update a mapping for a specific page without perturbing the mapping for other pages. -- MST
