Re: [Qemu-devel] [PATCH] sh4: define explicitly that the target CPU is 32 bit

["Blue Swirl" <blauwirbel@gmail.com>]

On 11/30/07, Paul Brook <paul@codesourcery.com> wrote:
> On Friday 30 November 2007, Carlo Marcelo Arenas Belon wrote:
> > On Fri, Nov 30, 2007 at 04:28:09PM +0000, Paul Brook wrote:
> > > On Friday 30 November 2007, Carlo Marcelo Arenas Belon wrote:
> > > > The following patch enforces that the sh4 target is 32 bit to prevent
> > > > qemu to expand incorrectly to a 64 bit wide cpu if compiled in a 64 bit
> > > > host.
> > >
> > > This is wrong. As the comment in cpu-defs.h says, target_phys_addr_t may
> > > need to be bigger than the actual target address space.
> > >
> > > What exactly are you trying to fix?
> >
> > in a generic way, that the CPU width of the host (as defined by the size of
> > the type that is used to store a target_phys_addr_t) that is used to build
> > the emulator affects in any way the size of the emulated target physical
> > address size or its representation.
> >
> > in the sh4 specific case, it doesn't make sense for sh4 to print an access
> > error to a physical address that is 64 bit long when it is a 32 bit CPU and
> > that is what would happen unless the patch is applied.
> >
> > if anything the following definition from cpu-defs.h is invalid for a
> > representation of a 32 bit physical address :
> >
> > #define TARGET_FMT_plx "%016" PRIx64
>
> Before you can fix that you probably need to fix the bits of qemu (TLB code)
> that store a host pointer in a phys_addr_t. Or at least distance
> TARGET_PHYS_ADDR_BITS from the definition of phys_addr_t, and include
> appropriate comments.
>
> In that case TARGET_PHYS_ADDR_BITS could be a precise value, rather than the
> next multiple of 32. e.g. I think sparc32 has a 40-bit physical address
> space.

36 bits. ASI bits could be included to address bits in order to
simplify the ASI handling, then the sum would be 43 or 44.