Re: [Qemu-devel] Potential sparc32 MMU bug

["Peter Creath" <pjcreath@gmail.com>]

By banging on get_physical_address, I was able to confirm that qemu
will properly assert an exception if the VM's MMU believes the page is
read-only.

How does env->mmuregs[] get mapped to the VM's MMU?  I would normally
write this off as an OpenBIOS bug, but it seems like bad behavior for
an emulator to silently suppress all such access violations.  At least
there should be a way to turn the suppression off for debugging -- or
at least a way for QEMU to log the suppressed error.

Is there such a way that I've missed?


On 2/16/07, Peter <pjcreath+openbios@gmail.com> wrote:
> Where is the policy of silently ignoring ROM writes implemented?  It
> may not be the proper behavior for sparc, and I'd like to tinker with
> it.  I'm just not sure where the write is getting suppressed (or,
> alternatively, where the exception is getting suppressed).
>
> On 2/16/07, Paul Brook <paul@codesourcery.com> wrote:
> > > > I don't know about sparc, but it's normal for writes to ROM to be
> > > > ignored. However by my reading the sparc bios is loaded into RAM anyway,
> > > > so it shouldn't matter.
> > >
> > > It definitely gets blocked by something: if I leave the the trap table
> > > in the .text section, the write silently fails.  If I move the trap
> > > table to the .data section, the write succeeds.  If I move the trap
> > > table over to .rodata, the write fails again.  What are you looking at
> > > that suggests the whole sparc bios is loaded read/write?
> >
> > I was mistaken. There is a ROM area defined, it's just the elf loader doesn't
> > care whether it's loading to rom or ram.
> >
> > My comment about rom writes being silently ignored still applies.
> >
> > Paul
> >
> >
>