[Qemu-devel] IO_MEM_NB_ENTRIES limit

[andrzej zaborowski]

Hi,

the maximum number of memory-mapped IO regions in qemu is
IO_MEM_NB_ENTRIES which is defined using TARGET_PAGE_BITS.  Due to
tiny pages available on ARM, IO_MEM_NB_ENTRIES is only 64 there.
OMAP2 cpu has many more logical IO regions than 64 and it makes sense
to register them as separate.

To be able to set IO_MEM_NB_ENTRIES higher, the io region index and
the address bits would have to be stored in separate fields in
PhysPageDesc and in CPUTLBEntry structs, instead of io index being
stored in the lower bits of addresses.  This would double the size of
both structs.  I'd like to hear if there are any other ideas for
removing the upper limit for IO_MEM_NB_ENTRIES.

I merged the main part of N800 machine support, which uses a OMAP2,
and it currently doesn't work in the form it's in SVN due to this
limitation.  I use the patch which is attached to the mail to remove
the IO_MEM_NB_ENTRIES dependency on TARGET_PAGE_BITS, but this is a
bad hack. It likely breaks IO_MEM_ROMD.

Regards
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iomemhack.patch
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