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Date: Thu, 7 Nov 2013 14:04:08 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH for-1.7 v2 1/8] exec: declare
 TARGET_PHYS_ADDR_SPACE_MAX to limit memory regions rendered by exec
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Alexander Graf <agraf@suse.de>, Eduardo Habkost <ehabkost@redhat.com>, Marcel Apfelbaum <marcel.a@redhat.com>, Jan Kiszka <jan.kiszka@siemens.com>, QEMU Developers <qemu-devel@nongnu.org>, Luiz Capitulino <lcapitulino@redhat.com>, Anthony Liguori <aliguori@amazon.com>, Paolo Bonzini <pbonzini@redhat.com>, Andreas =?iso-8859-1?Q?F=E4rber?= <afaerber@suse.de>

On Thu, Nov 07, 2013 at 10:49:50AM +0000, Peter Maydell wrote:
> On 7 November 2013 10:41, Marcel Apfelbaum <marcel.a@redhat.com> wrote:
> > The page table logic in exec.c assumes
> > that memory addresses are at most TARGET_PHYS_ADDR_SPACE_BITS.
> > Use TARGET_PHYS_ADDR_SPACE_MAX as max size for memory regions
> > rendered by exec.
> >
> > Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
> > ---
> >  include/exec/address-spaces.h | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/include/exec/address-spaces.h b/include/exec/address-spaces.h
> > index 3d12cdd..174cc05 100644
> > --- a/include/exec/address-spaces.h
> > +++ b/include/exec/address-spaces.h
> > @@ -23,6 +23,10 @@
> >
> >  #ifndef CONFIG_USER_ONLY
> >
> > +#define TARGET_PHYS_ADDR_SPACE_MAX                         \
> > +    (TARGET_PHYS_ADDR_SPACE_BITS == 64 ?                   \
> > +    UINT64_MAX : (0x1ULL << TARGET_PHYS_ADDR_SPACE_BITS))
> > +
> 
> I think it's worth adding a comment that this is a
> size intended for use in memory_region_init() calls and
> so follows the odd convention used by that API that
> it is a size in bytes with the exception that UINT64_MAX
> represents 2^64.
> 
> (it follows from this that using the #define anywhere
> except in a memory_region_init() call is probably a bug)
> 
> -- PMM

BTW how about we change the API to pass in int128?
Not for 1.7 of course.

This will help make sure it's only used for MRs.

-- 
MST