On Thu, Nov 06, 2014 at 04:10:15PM +0000, Burakov, Anatoly wrote: > Well, removing --base-virtaddr is not what I'm asking about. > > The issue at hand here is that, given our secondary process mechanism (that > you don't like :-) ), some stuff may be attempted to be mapped into space a > secondary process may already have mapped something else into (some > libraries, for example). This issue was originally discovered by OVDK, so we > added a --base-virtaddr option to try and map hugepages at exact virtual > address, rather than wherever mmap decides to do so on its own. > > The issue encountered by Liang (the author of the patch) is similar, only > it's not the hugepages are mapped into the occupied space, but rather the PCI > resources (which are mapped with NULL by default, so can be mapped anywhere). > Therefore he suggested a patch that maps the PCI resources into a space just > after the last hugepage when --base-virtaddr is provided. I'm not sure we > need the dependence on --base-virtaddr though, it can probably be done > unconditionally. If you have no opinion on the matter, we can leave this > detail of the patch as it is, then. > > Also, I would suspect that if we are to modify where UIO resources are > mapped, VFIO code should be modified the same way to avoid inconsistency > between the two. >
I find nothing wrong with your logic, Anatoly, it makes sense to me. :-) I'm curious, however, as to what Thomas has in mind for how we might improve the base-virtaddr flag. /Bruce > Thanks, > Anatoly > > -----Original Message----- > From: Thomas Monjalon [mailto:thomas.monjalon at 6wind.com] > Sent: Thursday, November 6, 2014 3:58 PM > To: Burakov, Anatoly > Cc: lxu; dev at dpdk.org; De Lara Guarch, Pablo > Subject: Re: [PATCH v5] eal: map uio resources after hugepages when the > base_virtaddr is configured. > > 2014-11-06 15:41, Burakov, Anatoly: > > Thomas, do we need to do similar changes to VFIO code, to keep consistency? > > Also, do we really need for this to depend on --base-virtaddr? Why not > > do it unconditionally, i.e. map PCI resources right after hugepages in > > memory? > > I don't really like the secondary process mechanism at all. > So I won't give good advice here ;) > But I feel this option --base-virtaddr should be improved or removed. > > -- > Thomas
