[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-block] [Xen-devel] [PATCH 2/4] block/xen_disk: remove use of g
From: |
Roger Pau Monné |
Subject: |
Re: [Qemu-block] [Xen-devel] [PATCH 2/4] block/xen_disk: remove use of grant map/unmap |
Date: |
Mon, 30 Apr 2018 16:28:26 +0100 |
User-agent: |
NeoMutt/20180323 |
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 <address@hidden>
> > Cc: address@hidden; address@hidden; qemu-
> > address@hidden; Anthony Perard <address@hidden>; Kevin
> > Wolf <address@hidden>; Stefano Stabellini <address@hidden>; Max
> > Reitz <address@hidden>
> > 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?
Roger.