Messages in this thread | | | Subject | Re: [PATCH RFC] uaccess: user_access_begin_after_access_ok() | From | Jason Wang <> | Date | Wed, 3 Jun 2020 13:18:54 +0800 |
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On 2020/6/3 下午12:18, Al Viro wrote: > On Wed, Jun 03, 2020 at 11:57:11AM +0800, Jason Wang wrote: > >>> How widely do you hope to stretch the user_access areas, anyway? >> >> To have best performance for small packets like 64B, if possible, we want to >> disable STAC not only for the metadata access done by vhost accessors but >> also the data access via iov iterator. > If you want to try and convince Linus to go for that, make sure to Cc > me on that thread. Always liked quality flame... > > The same goes for interval tree lookups with uaccess allowed. IOW, I _really_ > doubt that it's a good idea.
I see. We are just seeking an approach to perform better in order to compete with userspace dpdk backends.
I tried another approach of using direct mapping + mmu notifier [1] but the synchronization with MMU notifier is not easy to perform well.
[1] https://patchwork.kernel.org/patch/11133009/
> >>> Incidentally, who had come up with the name __vhost_get_user? >>> Makes for lovey WTF moment for readers - esp. in vhost_put_user()... >> >> I think the confusion comes since it does not accept userspace pointer (when >> IOTLB is enabled). >> >> How about renaming it as vhost_read()/vhost_write() ? > Huh? > > __vhost_get_user() is IOTLB remapping of userland pointer. It does not access > userland memory. Neither for read, nor for write. It is used by vhost_get_user() > and vhost_put_user(). > > Why would you want to rename it into vhost_read _or_ vhost_write, and in any case, > how do you give one function two names? IDGI...
I get you know, I thought you're concerning the names of vhost_get_user()/vhost_put_user() but actually __vhost_get_user().
Maybe something like __vhost_fetch_uaddr() is better.
Thanks
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