On Mon, Jul 04, 2016 at 04:19:20PM +0800, Xiao Guangrong wrote: > > > On 07/04/2016 03:53 PM, Neo Jia wrote: > >On Mon, Jul 04, 2016 at 03:37:35PM +0800, Xiao Guangrong wrote: > >> > >> > >>On 07/04/2016 03:03 PM, Neo Jia wrote: > >>>On Mon, Jul 04, 2016 at 02:39:22PM +0800, Xiao Guangrong wrote: > >>>> > >>>> > >>>>On 06/30/2016 09:01 PM, Paolo Bonzini wrote: > >>>>>The vGPU folks would like to trap the first access to a BAR by setting > >>>>>vm_ops on the VMAs produced by mmap-ing a VFIO device. The fault handler > >>>>>then can use remap_pfn_range to place some non-reserved pages in the VMA. > >>>> > >>>>Why does it require fetching the pfn when the fault is triggered rather > >>>>than when mmap() is called? > >>> > >>>Hi Guangrong, > >>> > >>>as such mapping information between virtual mmio to physical mmio is only available > >>>at runtime. > >> > >>Sorry, i do not know what the different between mmap() and the time VM actually > >>accesses the memory for your case. Could you please more detail? > > > >Hi Guangrong, > > > >Sure. The mmap() gets called by qemu or any VFIO API userspace consumer when > >setting up the virtual mmio, at that moment nobody has any knowledge about how > >the physical mmio gets virtualized. > > > >When the vm (or application if we don't want to limit ourselves to vmm term) > >starts, the virtual and physical mmio gets mapped by mpci kernel module with the > >help from vendor supplied mediated host driver according to the hw resource > >assigned to this vm / application. > > Thanks for your expiation. > > It sounds like a strategy of resource allocation, you delay the allocation until VM really > accesses it, right? Yes, that is where the fault handler inside mpci code comes to the picture. Thanks, Neo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
