Re: [Qemu-devel] [PATCH] Add MIPS ELF loader

[Thiemo Seufer]

On Thu, Mar 30, 2006 at 03:40:25PM +0200, Dirk Behme wrote:
> Thiemo Seufer wrote:
> >On Tue, Mar 28, 2006 at 08:57:15AM +0200, Dirk Behme wrote:
> >>What about the patch in attachment? It first tries to load
> >>image as an ELF file. If this fails it falls back to raw
> >>image load. Additionally, it takes feature of patch above to
> >>go on even if no BIOS is found.
> >
> >
> >A slightly more polished version with less noisy messages is appended.
> >It also adjusts the ramdisk load address to physical addressing,
> >similiar to the binary kernel load.
> 
> One question I just found:
> 
> If we go on if no BIOS is found/executed and we load some 
> stuff to e.g. 0x80010000, where is the default address 
> translation made? As I understand MIPS, code in kseg0 
> (0x80000000) and kseg1 (0xA0000000) should be executable 
> without MMU/TLB setup because it is mapped by default to 
> physical 0x0. But looks to me that I get a
> 
> cpu_mips_handle_mmu_fault pc 80010000 ad 80010000 rw 2 
> is_user 0 smmu 1

That comes not from the MIPS TLB mapping (which is for KSEG0/1 a fixed
translation involving the high bits) but the underlying qemu softmmu
support.

The whole thing works but eats significant performance, there should
be room for improvements.


Thiemo