Re: [GXemul-devel] NetBSD/hpcmips install fails under GXemul 0.6.1

[Anders G. <ga...@gm...>]

Andreas: Can you try changing the if statement in this block in
src/cpus/cpu_mips_coproc.cc in 0.6.1:

...
                /*
                 *  If we have a memblock (host page) for the physical page,
                 *  then add a translation for it immediately, to save some
                 *  time. (It would otherwise be added later on anyway,
                 *  because of a translation miss.)
                 *
                 *  NOTE/TODO: This is only for 4KB pages so far. It would
                 *             be too expensive to add e.g. 16MB pages like
                 *             this.
                 */
                if (psize == 0x1000) {
                        memblock = memory_paddr_to_hostaddr(cpu->mem,
paddr0, 0);
                        if (memblock != NULL && cp->reg[COP0_ENTRYLO0] &
ENTRYLO_V)
                                cpu->update_translation_table(cpu, vaddr0,
memblock,
                                    wf0, paddr0);
                        memblock = memory_paddr_to_hostaddr(cpu->mem,
paddr1, 0);
                        if (memblock != NULL && cp->reg[COP0_ENTRYLO1] &
ENTRYLO_V)
                                cpu->update_translation_table(cpu, vaddr1,
memblock,
                                    wf1, paddr1);
                }

to

                if (psize == 0x1000 && cpu->cd.mips.cpu_type.rev !=
MIPS_R4100) {

and see if that works as a short-term hack? I tried it here, and it seemed
to work.

I have no idea why. I assumed that page size 1 KB would be problematic, not
4 KB. So perhaps this just hides the bug...


Anders

On Sat, Jun 1, 2019 at 11:03 AM Anders Gavare <ga...@gm...> wrote:

> > Hi,
> > GXemul 0.6.1 is having trouble installing NetBSD/hpcmips.
> > More details here:
> > http://gnats.netbsd.org/54252
>
> Hi Andreas,
>
> I think I may have found the revision where this broke.
>
> ------------------------------------------------------------------------
> r5906 | debug | 2018-06-13 15:13:23 +0200 (Wed, 13 Jun 2018) | 1 line
>
> Fixing an old TODO for invalidating translation caches when using non-4KB
> pages for MIPS. This makes HelenOS 0.7.1/malta boot further than before.
> ------------------------------------------------------------------------
>
> At least on my machine, installing NetBSD 8.0 and booting after install to
> a working login as root worked fine up to revision 5905, but not with 5906
> and forward.
>
> (Except for the usual problem of /dev/ttyE0 not being enabled by default,
> so login via serial console doesn't work "out of the box".)
>
> I will investigate that fix, and see if it can be done some other way.
>
> A wild guess as to the cause of the bug: The VR4121 has 1 KB pages which I
> guess are buggy in GXemul. I don't know how much of that NetBSD uses in
> practice, perhaps it mostly uses 4 KB pages.
>
> Also, this is a good opportunity to clean up the GXemul documentation and
> create up-to-date regression testing scripts for hpcmips; many of the modes
> (MobilePro 770, 800, and 880) seem to have bit-rotted over time when
> booting NetBSD with -X. Most likely due to incompleteness of emulation.
> These modes only seem to work with serial console these days. Luckily,
> MobilePro 780 emulation still works with both serial and graphical console.
> :-)
>
>
> Anders
>
>