Re: [Qemu-devel] Help - `flush_icache_range' MacPPC

[Alexander Graf]

On 09.02.2012, at 00:29, Scott Wood wrote:

> On 02/07/2012 04:57 PM, Alexander Graf wrote:
>> 
>> On 07.02.2012, at 23:29, Brad Smith wrote:
>> 
>>> On 07/02/12 5:12 PM, malc wrote:
>>>> On Tue, 7 Feb 2012, Alexander Graf wrote:
>>>> 
>>>>> 
>>>>> On 07.02.2012, at 22:12, malc wrote:
>>>>> 
>>>>>> On Tue, 7 Feb 2012, Alexander Graf wrote:
>>>>>> 
>>>>>>> 
>>>>>>> On 07.02.2012, at 13:52, Maurizio Caloro wrote:
>>>>>>> 
>>>>>>>> Hello Together
>>>>>>>> Here i drive with me MiniMac G4 1.4Ghz and i try to run Qemu 1.0. i 
>>>>>>>> wan't run one Virt. MS Server2008 it's this realistic?.
>>>>>>>> 
>>>>>>>> Unfortunitly from the first (other) Mailinglist i don't become any 
>>>>>>>> Answer.
>>>>>>>> 
>>>>>>>> on a possible error recovery support, I would grateful to you.
>>>>>>>> Thanks and best regards
>>>>>>>> Mauri
>>>>>>>> 
>>>>>>>>> NetBSD powermac.G4 5.1 NetBSD 5.1 (GENERIC) #0: Sat Nov  6 17:09:11 
>>>>>>>>> UTC>2010  
>>>>>>>>> address@hidden:/home/builds/ab/netbsd-5-1->RELEASE/macppc/201011061943Z-obj/home/builds/ab/netbsd-5-1->RELEASE/src/sys/arch/macppc/compile/GENERIC
>>>>>>>>>  macppc
>>>>>>>>> 
>>>>>>>>> # gmake
>>>>>>>>> CC    i386-softmmu/memory.o
>>>>>>>>> LINK  i386-softmmu/qemu-system-i386
>>>>>>>>> ld: warning: libintl.so.0, needed by /usr/pkg/lib/libgthread-2.0.so, 
>>>>>>>>> may conflict with libintl.so.8
>>>>>>>>> tcg/tcg.o: In function `tcg_prologue_init':
>>>>>>>>> /usr/source/qemu-1.0/tcg/tcg.c:268: undefined reference to 
>>>>>>>>> `flush_icache_range'
>>>>>>>>> tcg/tcg.o: In function `ppc_tb_set_jmp_target':
>>>>>>>>> /usr/source/qemu-1.0/tcg/ppc/tcg-target.c:1291: undefined reference 
>>>>>>>>> to `flush_icache_range'
>>>>>>>>> tcg/tcg.o: In function `tcg_gen_code':
>>>>>>>>> /usr/source/qemu-1.0/tcg/tcg.c:2191: undefined reference to 
>>>>>>>>> `flush_icache_range'
>>>>>>> 
>>>>>>> I'd say your gcc is too old / buggy.
>>>>>> 
>>>>>> You probably missed the NetBSD part (anyway originally i did)
>>>>> 
>>>>> Gcc on NetBSD doesn't implement the cache flush helpers? They're just a
>>>>> bunch of instructions, so I don't see how that'd be target os specific.
>>>>> 
>>>> 
>>>> Take a look at cache-utils.c, it conditionally (depending on the host OS
>>>> type) tries to gigure out the cache line sizes, there's code to do that
>>>> on Linux, OSX, AIX and FreeBSD. I have no idea if FreeBSD method works
>>>> for Net/Open/Dragonfly.. so..
>>> 
>>> The FreeBSD method will not work with NetBSD. For NetBSD you have to use
>>> the machdep.cacheinfo sysctl MIB. For OpenBSD this is the only local patch
>>> we have since there is no sysctl (yet) to retrieve the cache line size.
>>> DragonFly has no PowerPC support.
>> 
>> Eh, this patch:
>> 
>> diff --git a/tcg/ppc/tcg-target.c b/tcg/ppc/tcg-target.c
>> index f5d9bf3..f9793e6 100644
>> --- a/tcg/ppc/tcg-target.c
>> +++ b/tcg/ppc/tcg-target.c
>> @@ -1260,6 +1260,17 @@ static void tcg_out_brcond2 (TCGContext *s, const 
>> TCGArg *args,
>>     tcg_out_bc (s, (BC | BI (7, CR_EQ) | BO_COND_TRUE), args[5]);
>> }
>> 
>> +#ifdef __NetBSD__
>> +static void flush_icache_range(unsigned long begin, unsigned long end)
>> +{
>> +    unsigned int i = begin & ~15UL;
>> +    for (; i < end; i+=16) {
>> +        asm("icbi 0,%0" : : "r"(i));
>> +    }
>> +    asm("isync");
>> +}
>> +#endif
> 
> What about flushing the data cache first, as the other
> flush_icache_range does?

I actually wrote this one from scratch. Ahem.

So why are we flushing the dcache on the other one? Does the icache always fill 
from memory or can it check if something's in the dcache and fetch it from 
there? If it's the former, then a dcache flush is crucial, right.

> Why isn't the cache-utils.h version of flush_icache_range being seen?
> It's only ppc_init_cacheline_sizes() that is OS-conditional -- shouldn't
> that be what the undefined reference is for?  Is _ARCH_PPC failing to be
> defined?

Oh, there is a cache flush function already there! Hah! I completely missed out 
on that one.

I would assume it's either because _ARCH_PPC is failing to be picked up 
(include order?) or because the header file is just not included. My motivation 
in digging into ppc NetBSD issues is rather small though.


Alex