Re: [Qemu-devel] Poking a sun4v machine

[Andreas Färber]

Am 30.04.2012 18:39, schrieb Artyom Tarasenko:
> Tried to boot QEMU Niagara machine with the firmware from the
> OpenSPARC T1 emulator ( www.opensparc.net/opensparc-t1/download.html )
> , and it dies very early.
> The reason: in translate.c
> 
> #define hypervisor(dc) (dc->mem_idx == MMU_HYPV_IDX)
> #define supervisor(dc) (dc->mem_idx >= MMU_KERNEL_IDX)
> 
> and the dc->mem_idx is initialized like this:
> 
>     if (env1->tl > 0) {
>         return MMU_NUCLEUS_IDX;
>     } else if (cpu_hypervisor_mode(env1)) {
>         return MMU_HYPV_IDX;
>     } else if (cpu_supervisor_mode(env1)) {
>         return MMU_KERNEL_IDX;
>     } else {
>         return MMU_USER_IDX;
>     }
> 
> Which seems to be conceptually incorrect. After reset tl == MAXTL, but
> still super- and hyper-visor bits are set, so both supervisor(dc) and
> hypervisor(dc) must return 1 which is impossible in the current
> implementation.
> 
> What would be the proper way to fix it? Make mem_idx bitmap, add two
> more variables to DisasContext, or ...?
> 
> Some other findings/questions:
> 
>     /* Sun4v generic Niagara machine */
>     {
>         .default_cpu_model = "Sun UltraSparc T1",
>         .console_serial_base = 0xfff0c2c000ULL,
> 
> Where is this address coming from? The OpenSPARC Niagara machine has a
> "dumb serial" at 0x1f10000000ULL.
> 
> And the biggest issue: UA2005 (as well as UA2007) describe a totally
> different format for a MMU TTE entry than the one sun4u CPU are using.
> I think the best way to handle it would be splitting off Niagara
> machine, and #defining MMU bits differently for sun4u and sun4v
> machines.
> 
> Do we the cases in qemu where more than two (qemu-system-xxx and
> qemu-system-xxx64) binaries are produced?
> Would the name qemu-system-sun4v fit the naming convention?

We have such a case for ppc (ppcemb) and it is kind of a maintenance
nightmare - I'm working towards getting rid of it with my QOM CPU work.
Better avoid it for sparc in the first place.

Instead, you should add a callback function pointer to SPARCCPUClass
that you initialize based on CPU model so that is behaves differently at
runtime rather than at compile time.
Or if it's just about the class_init then after the Hard Freeze I can
start polishing my subclasses for sparc so that you can add a special
class_init for Niagara.

Helpers such as cpu_hypervisor_mode() will need to be changed to take a
SPARCCPU *cpu rather than CPUSPARCState *env argument; as an interim
solution sparc_env_get_cpu() can be used. (examples on the list for sh4)

Andreas

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