On Mon, Jan 07, 2019 at 02:58:08PM +0800, Jason Wang wrote: > > On 2019/1/5 上午5:41, Michael S. Tsirkin wrote: > > On Sat, Dec 29, 2018 at 08:46:51PM +0800, Jason Wang wrote: > > > This series tries to access virtqueue metadata through kernel virtual > > > address instead of copy_user() friends since they had too much > > > overheads like checks, spec barriers or even hardware feature > > > toggling. > > > > I think it's a reasonable approach. > > However I need to look at whether and which mmu notifiers are invoked before > > writeback. Do you know? > > > I don't know but just looking at the MMU notifier ops definition, there's no > such callback if my understanding is correct. > > Thanks In that case how are you making sure used ring updates are written back? If they aren't guest will crash ... > > > > > > Test shows about 24% improvement on TX PPS. It should benefit other > > > cases as well. > > > > > > Changes from V2: > > > - fix buggy range overlapping check > > > - tear down MMU notifier during vhost ioctl to make sure invalidation > > > request can read metadata userspace address and vq size without > > > holding vq mutex. > > > Changes from V1: > > > - instead of pinning pages, use MMU notifier to invalidate vmaps and > > > remap duing metadata prefetch > > > - fix build warning on MIPS > > > > > > Jason Wang (5): > > > vhost: generalize adding used elem > > > vhost: fine grain userspace memory accessors > > > vhost: rename vq_iotlb_prefetch() to vq_meta_prefetch() > > > vhost: introduce helpers to get the size of metadata area > > > vhost: access vq metadata through kernel virtual address > > > > > > drivers/vhost/net.c | 4 +- > > > drivers/vhost/vhost.c | 416 +++++++++++++++++++++++++++++++++++++----- > > > drivers/vhost/vhost.h | 15 +- > > > 3 files changed, 384 insertions(+), 51 deletions(-) > > > > > > -- > > > 2.17.1
