Re: [Xen-devel] [RFC][PATCH 1/6] HVM PCI Passthrough (non-IOMMU)

[Muli Ben-Yehuda <muli@xxxxxxxxxx>]

On Mon, Jun 04, 2007 at 05:43:02PM -0400, Guy Zana wrote:
>  
> 
> > -----Original Message-----
> > From: Muli Ben-Yehuda [mailto:muli@xxxxxxxxxx] 
> > Sent: Monday, June 04, 2007 9:26 PM
> > To: Guy Zana
> > Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> > Subject: Re: [Xen-devel] [RFC][PATCH 1/6] HVM PCI Passthrough 
> > (non-IOMMU)
> > 
> > > +
> > > +# PCI pass-through flags
> > > +mapping_1to1 ?= y
> > > +passthrough ?= y
> > 
> > Does one make sense without the other?
> 
> Actually yes, you'll need the 1:1 layout only when using devices
> that needs DMA.  Just the passthorugh switch could be turned on for
> other devices...

I think we take it as a given that passthrough (whether through 1:1 or
IOMMU support) will be compiled into Xen, so no need for a separate
flag.

> > >  XEN_COMPILE_ARCH    ?= $(shell uname -m | sed -e s/i.86/x86_32/ \
> > >                           -e s/ppc/powerpc/ -e s/i86pc/x86_32/)
> > > @@ -9,7 +13,7 @@ XEN_OS              ?= $(shell uname -s)
> > >  XEN_OS              ?= $(shell uname -s)
> > >  
> > >  ifeq ($(XEN_TARGET_ARCH),x86_32)
> > > -XEN_TARGET_X86_PAE  ?= y
> > > +XEN_TARGET_X86_PAE  ?= n
> > 
> > Is there a dependency between 1-1 / passthrough and !PAE, or 
> > is this just for convenience?
> 
> There is a dependency, not that it's that a problem to support PAE,
> we just didn't implement it yet.  We decided to support x86_64 and
> remove the x86_32 / PAE support, as we see it, there is just no need
> to support x86_32 / PAE anymore...

Ok, just for reference, if there's a dependency in the future, it
should be expressed that way (only turn on PAE if 1:1 is on, in this
case).

> > >  endif
> > >  
> > >  CONFIG_$(XEN_OS) := y
> > > --- a/tools/Rules.mk      Sat May 05 13:48:05 2007 +0100
> > > +++ b/tools/Rules.mk      Thu May 31 21:04:53 2007 +0300
> > > @@ -13,6 +13,14 @@ X11_LDPATH = -L/usr/X11R6/$(LIBDIR)  
> > X11_LDPATH = 
> > > -L/usr/X11R6/$(LIBDIR)
> > >  
> > >  CFLAGS += -D__XEN_TOOLS__
> > > +
> > > +ifeq ($(passthrough),y)
> > > +    CFLAGS += -DCONFIG_NEO
> > > +endif
> > 
> > You probably want a better name than CONFIG_NEO, much to the 
> > disappointment of matrix fans everywhere.
> 
> Hehe :)
> It'll be removed completely.
> The 1:1 enabled layout will be controlled by a boot parameter.

Ok, good.

Cheers,
Muli

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