> -----Original Message----- > From: Roger Pau Monne > Sent: 30 April 2018 16:28 > To: Paul Durrant <paul.durr...@citrix.com> > Cc: xen-de...@lists.xenproject.org; qemu-block@nongnu.org; qemu- > de...@nongnu.org; Anthony Perard <anthony.per...@citrix.com>; Kevin > Wolf <kw...@redhat.com>; Stefano Stabellini <sstabell...@kernel.org>; Max > Reitz <mre...@redhat.com> > Subject: Re: [Xen-devel] [PATCH 2/4] block/xen_disk: remove use of grant > map/unmap > > On Mon, Apr 30, 2018 at 04:16:52PM +0100, Paul Durrant wrote: > > > -----Original Message----- > > > From: Roger Pau Monne > > > Sent: 30 April 2018 16:12 > > > To: Paul Durrant <paul.durr...@citrix.com> > > > Cc: xen-de...@lists.xenproject.org; qemu-block@nongnu.org; qemu- > > > de...@nongnu.org; Anthony Perard <anthony.per...@citrix.com>; > Kevin > > > Wolf <kw...@redhat.com>; Stefano Stabellini <sstabell...@kernel.org>; > Max > > > Reitz <mre...@redhat.com> > > > Subject: Re: [Xen-devel] [PATCH 2/4] block/xen_disk: remove use of > grant > > > map/unmap > > > > > > On Mon, Apr 30, 2018 at 01:01:37PM +0100, Paul Durrant wrote: > > > > The grant copy operation was added to libxengnttab in Xen 4.8.0. If > grant > > > > copy is available then data from the guest will be copied rather than > > > > mapped. > > > > The xen_disk source can be significantly simplified by removing this > now > > > > redundant code. > > > > > > Hm, I know this is a PITA, but FreeBSD gntdev hasn't implemented the > > > grant-copy operation yet. > > > > > > I could try to implement it, but I can't make any promises on the time > > > ATM, since I'm quite busy. > > > > > > > I guess we could carry a compat patch in QEMU that implements grant copy > by doing a map/memcpy/unmap , but QEMU feels like the wrong place for > that. I could try putting together a similar patch for the freebsd.c component > of libxengnttab in the xen source rather than it simply failing with ENOSYS as > it does now. Would either of those help? > > Maybe this could be implemented in gnttab_core.c, so it can also be > used by MiniOS and Linux versions not supporting the copy ioctl as a > fallback?
That sounds like a reasonable idea. I'll put something together so that it can go in early in 4.12. Paul > > Roger.
