Re: [Qemu-devel] Mips target '-kernel' option bug

[Thiemo Seufer]

J. Mayer wrote:
> On Wed, 2007-10-17 at 22:06 +0300, Blue Swirl wrote:
> > On 10/17/07, Jocelyn Mayer <address@hidden> wrote:
> > > On Wed, 2007-10-17 at 14:51 +0100, Thiemo Seufer wrote:
> > > > J. Mayer wrote:
> > > > > I failed to run Mips target test image on my amd64 machine and I now
> > > > > found the reason of the bug:
> > > > > the kernel loader code used in hw/mips_r4k.c and hw/mips_malta.c
> > > > > implicitelly assumes that the ram_addr_t is 32 bits long.
> > > > > Unfortunatelly, on 64 bits hosts, this won't be the case and the 
> > > > > kernel
> > > > > load address then is over 4 GB. Then, when computing the 
> > > > > initrd_offset,
> > > > > the code always concludes that there's not enough RAM available to 
> > > > > load
> > > > > it at the top of the kernel.
> > > > > I found 2 ways of fixing the bug, but I don't know which one is 
> > > > > correct
> > > > > in Mips execution environment.
> > > > > The first patch is to make the VIRT_TO_PHYS_ADDEND negative, thus
> > > > > translating the kernel virtual address from 0x8000nnnn to the physical
> > > > > one 0x0000nnnn (instead of 0x10000nnnn, when running on 64 bits 
> > > > > hosts).
> > > > > The second solution would be to explicitelly always cast the 
> > > > > kernel_high
> > > > > value to 32 bits.
> > > > > As I do not really know if some Mips target specific constraints would
> > > > > make one of the other solution prefered, I'd better let the specialist
> > > > > choose !
> > > > >
> > > > > The good news is that, once this issue is fixed, the Mips test images
> > > > > run with the reverse-endian softmmu patch applied.
> > > >
> > > > I think this patch is the correct fix. Please test and comment.
> > >
> > > Thanks, I'll test it at home tonight.
> > > To satisfy my curiosity, is there a specific reason to have a positive
> > > VIRT_TO_PHYS_ADDEND ?
> > 
> > On Sparc, OpenBIOS image is loaded to a physical address that is
> > higher in the address space than the virtual address:
> > #define PROM_PADDR           0xff0000000ULL
> > #define PROM_VADDR           0xffd00000
> > and
> > #define PROM_ADDR            0x1fff0000000ULL
> > #define PROM_VADDR           0x000ffd00000ULL
> 
> OK, thanks.
> And the patch seems OK for me, it may be a good idea to commit it !

Committed.


Thiemo