Hi Bob On Thu, Dec 14, 2017 at 02:07:38PM +0800, Bob Liu wrote: > On 2017/12/14 11:38, Lu Baolu wrote: > >>>> We already have an existing MMU notifiers for userspace updates, > >>>> however we lack the same thing for kernel page table updates. To > >> Sorry, I didn't get which situation need this notification. > >> Could you please describe the full scenario? > > > > Okay. > > > > 1. When an SVM capable driver calls intel_svm_bind_mm() with > > SVM_FLAG_SUPERVISOR_MODE set in the @flags, the kernel > > memory page mappings will be shared between CPUs and > > the DMA remapping agent (a.k.a. IOMMU). The page table > > entries will also be cached in both IOTLB (located in IOMMU) > > and the DEVTLB (located in device). > > > > But who/what kind of real device has the requirement to access a kernel VA? > Looks like SVM_FLAG_SUPERVISOR_MODE is used by nobody? That's right, there is no inkernel user at the moment, but we certainly see them coming. Maybe not the best example :-), but I'm told Lustre and some of the modern NIC's also can benefit from SVM in kernel use. Not a hypothetical use case certainly! Cheers, Ashok -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
