On 14/06/18 12:21, Jan Beulich wrote: >>>> On 14.06.18 at 10:48, <jgr...@suse.com> wrote: >> On 14/06/18 10:17, Julien Grall wrote: >>> On Thu, 14 Jun 2018, 07:40 Juergen Gross, <jgr...@suse.com >>> <mailto:jgr...@suse.com>> wrote: >>> >>> On 13/06/18 18:25, Andrew Cooper wrote: >>> > On 13/06/18 16:27, Juergen Gross wrote: >>> >>> Looking more into the privcmd driver I'm rather sure now I can solve >>> this via mmap() plus an ioctl(). So the kernel would allocate the >>> bounce buffers and map them into user space. This will require changes >>> only in libxencall without having to modify its external interface. >>> >>> >>> It looks like David Vrabel sent in 2016 a patch implementing that >>> solution [1]. It seems it has not been merged. Do you have any insight >>> why it was not merged? >> >> No. It had all needed Acks and there were no open questions. >> >> Thanks for the reference, I think I can just reuse the patch after some >> rebasing. > > But I still wonder whether retaining references obtained through > get_user_pages_fast() across system calls is a legitimate thing to do.
As discussed on IRC I've decided to add just another device node which can be used to mmap() a hypercall buffer with all needed attributes. David's patch seemed to be overkill for the few buffers normally being allocated (for domain creation the maximum was 3 single page buffers in a small test I did). Juergen _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
