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Re: [Qemu-ppc] [Qemu-devel] [PATCH v2] PPC: Clean up DECR implementation
From: |
Alexander Graf |
Subject: |
Re: [Qemu-ppc] [Qemu-devel] [PATCH v2] PPC: Clean up DECR implementation |
Date: |
Wed, 9 Apr 2014 21:59:41 +0200 |
> Am 09.04.2014 um 21:33 schrieb Tom Musta <address@hidden>:
>
>> On 4/8/2014 2:58 PM, Alexander Graf wrote:
>>> On 04/08/2014 09:56 PM, Tom Musta wrote:
>>> On 4/6/2014 3:55 PM, Alexander Graf wrote:
>>> <snip>
>>>
>>>> @@ -806,6 +838,10 @@ clk_setup_cb cpu_ppc_tb_init (CPUPPCState *env,
>>>> uint32_t freq)
>>>> tb_env = g_malloc0(sizeof(ppc_tb_t));
>>>> env->tb_env = tb_env;
>>>> tb_env->flags = PPC_DECR_UNDERFLOW_TRIGGERED;
>>>> + if (env->insns_flags & PPC_SEGMENT_64B) {
>>>> + /* All Book3S 64bit CPUs implement level based DEC logic */
>>>> + tb_env->flags |= PPC_DECR_UNDERFLOW_LEVEL;
>>>> + }
>>>> /* Create new timer */
>>>> tb_env->decr_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
>>>> &cpu_ppc_decr_cb, cpu);
>>>> if (0) {
>>> Equating Book3S with PPC_SEGMENT_64B is clever ... is it too clever?
>>> Especially since
>>> the SLB Bridge is in the phased-out category and consequently we should
>>> expect future
>>> Book3S implementations to not support this instruction category.
>>
>> Maybe it's too clever :). I'm very open to suggestions on how to figure this
>> out otherwise. Or maybe we should just rework the way timers get created and
>> make them be part of the core itself?
>>
>>
>> Alex
>
> A somewhat more practical approach than redesigning timer init: The phrasing
> introduced into Book3S
> that corresponds to your UNDERFLOW_LEVEL flag has existed at least since ISA
> 2.03. And 2.03 introduced
> some new features, like SPE and Altivec. So ...
e6500 supports Altivec :)
>
> if (env->insns_flags & (PPC_SEGMENT_64B | PPC_SPE | PPC_ALTIVEC)) {
> /* All Book3S 64bit CPUs implement level based DEC logic */
> tb_env->flags |= PPC_DECR_UNDERFLOW_LEVEL;
> }
>
> would catch a few more. I'm not sure we get into this code for Book3E
> machines, but if you are worried
> about that you could also ensure that insns_flags doesn't have PPC_BOOKE on.
Phew, I'm not quite sure. We can do it as an interim solution, but really the
timer is a core property rather than a machine device :). So eventually this
should get reworked.
Alex