On Wed, Jan 08, 2025 at 09:30:26AM -0400, Jason Gunthorpe wrote: > On Tue, Jan 07, 2025 at 10:27:15PM +0800, Xu Yilun wrote: > > Add a flag for ioctl(VFIO_DEVICE_BIND_IOMMUFD) to mark a device as > > for private assignment. For these private assigned devices, disallow > > host accessing their MMIO resources. > > Why? Shouldn't the VMM simply not call mmap? Why does the kernel have > to enforce this? MM.. maybe I should not say 'host', instead 'userspace'. I think the kernel part VMM (KVM) has the responsibility to enforce the correct behavior of the userspace part VMM (QEMU). QEMU has no way to touch private memory/MMIO intentionally or accidently. IIUC that's one of the initiative guest_memfd is introduced for private memory. Private MMIO follows. Thanks, Yilun > > Jason
