On Thu, 2014-06-05 at 13:56 +0200, Alexander Graf wrote: > What if we ask user space to give us a pointer to user space allocated > memory along with the TCE registration? We would still ask user space to > only use the returned fd for TCE modifications, but would have some > nicely swappable memory we can store the TCE entries in. That isn't going to work terribly well for VFIO :-) But yes, for emulated devices, we could improve things a bit, including for the 32-bit TCE tables. For emulated, the real mode path could walk the page tables and fallback to virtual mode & get_user if the page isn't present, thus operating directly on qemu memory TCE tables instead of the current pinned stuff. However that has a cost in performance, but since that's really only used for emulated devices and PAPR VIOs, it might not be a huge issue. But for VFIO we don't have much choice, we need to create something the HW can access. > In fact, the code as is today can allocate an arbitrary amount of pinned > kernel memory from within user space without any checks. Right. We should at least account it in the locked limit. Cheers, Ben. -- 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
