Re: [Xen-devel] Re: [GIT PULL] pv/pcifront-2.6.32

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 03/02/2010 01:54 PM, Konrad Rzeszutek Wilk wrote:
> On Tue, Mar 02, 2010 at 12:12:23PM -0800, Jeremy Fitzhardinge wrote:
>    
> > On 03/01/2010 07:12 PM, Konrad Rzeszutek Wilk wrote:
> >      
> > > Hey Jeremy,
> > >
> > > Please pull from
> > > git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen.git pv/pcifront-2.6.32
> > >
> > > It is a back-port of the Xen PCI front driver (not the SR-IOV one, just
> > > old plain one). It has been tested with a bare 2.6.32 tree
> > > (pv/master.2.6.32) and with xen/next
> > >
> > > The merge of this is a bit hairy, so I did my own which is available in
> > > the pv/xen.next.merge (which is basically xen/next + pv/pcifront-2.6.32
> > > + pv/fbfbront + xen: Allow unprivileged Xen domains to create iomap
> > > pages).
> > >
> > >        
> > I did a separate merge of the fbfront branch.  Can you do another merge
> > with just the pcifront stuff?
> >      
> Done: pv/merge.xen.next
>    
> > (BTW, do you use git rerere?  It remembers the results of previous merge
> > resolutions and will apply them again if you re-merge.)
> >      
> Oooh goodies. Will start using it.
>    
> >      
> > > To make the PCI front driver work, another patch has to be put added in
> > > the xen/next (or better yet in the swiotlb - but it really does not seem
> > > to fit there), which is the "xen: Allow unprivileged Xen domains to
> > > create iomap pages" (5a7357bdb10b40414d97d7582f5467e4a709bd07)
> > >
> > >        
> > Do we really need that patch any more?  The comment doesn't seem to bear
> > any relationship to its contents any more; it talks about disallowing
> > ISA mappings, but all it does it mask write-through/uncachable from PTEs
> > for non-privileged domains, and I'm not sure that's even desirable.  I
> > think Xen will mask those flags from the PTE if the domain isn't allowed
> > to touch the device, and we want to be able to let passthrough mappings
> > to be uncached or writethrough.
> >
> > Do things break without it?
> >      
> I needed it for v2.6.32 + jeremy/xen/dom0/konrad-swiotlb-2.6.32 +
> konrad/pv/pcifront-2.6.32. Otherwise I would get this:
>    
OK, so I guess Xen does complain if you try to set UC/WT ptes but are 
non-privileged.  But still, with that patch in place, it means that even 
a passthrough hardware mapping may lack UC/WT.  Perhaps that doesn't 
matter?  I bet it will when we get around to fixing up PAT.
> _But_, with xen/next + pv/pcifront there was no need for it.
>    
That change is already present.

    J

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