Re: [Qemu-devel] [PATCH] MIPS: Fix dmtc0 instruction

[Aurelien Jarno <aurelien@aurel32.net>]

Thiemo Seufer a écrit :
> Aurelien Jarno wrote:
>> On Sat, Aug 23, 2008 at 06:42:34PM +0200, Hervé Poussineau wrote:
>>> Hi,
>>>
>>> In gen_dmtc0 function, TCG temporary variable t0 is freed at the end of
>>> the function. Variable is freed again in the gen_dmtc0 caller.
>>> I removed the free in gen_dmtc0, to do like in gen_dmfc0, gen_mfc0,
>>> gen_mtc0.
>>>
>>> Incidentally, this unregresses NetBSD on Pica 61.
>>  
>> This was also affecting Linux MIPS64 and I have noticed the problem this
>> morning (though it seems to be a few weeks old).
> 
> My old 64-bit testcase worked for some reason despite that bug. The current
> debian/testing kernel image for malta/5kc failed, though.
> 
>> I have applied the patch, and also removed another tcg_temp_free(t0)
>> which has been left. Thanks!
> 
> I can confirm it works here as well, thank you. However, I still see
> QEMU hang with the debian kernel at IDE detection:
> 
> [...]
> [    2.040127] pcnet32.c:v1.34-NAPI 14.Aug.2007 tsbogend@alpha.franken.de
> [    2.040127] pcnet32: PCnet/PCI II 79C970A at 0x1020, 52:54:00:12:34:56 assigned IRQ 10.
> [    2.040127] eth0: registered as PCnet/PCI II 79C970A
> [    2.040127] pcnet32: 1 cards_found.
> [    2.040127] Uniform Multi-Platform E-IDE driver
> [    2.040127] ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
> [    2.040127] PIIX4: IDE controller (0x8086:0x7111 rev 0x00) at  PCI slot 0000:00:0a.1
> [    2.040127] PCI: Enabling device 0000:00:0a.1 (0000 -> 0001)
> [    2.040127] PIIX4: not 100% native mode: will probe irqs later
> [    2.040127]     ide0: BM-DMA at 0x1040-0x1047, BIOS settings: hda:PIO, hdb:PIO
> [    2.040127]     ide1: BM-DMA at 0x1048-0x104f, BIOS settings: hdc:PIO, hdd:PIO
> 
> I figure CONFIG_NO_HZ has too high demands on the count/compare emulation.
> 

I don't have this problem. Are you sure it is related to CONFIG_NO_HZ?
AFAIK the problems with CONFIG_NO_HZ appear earlier, when computing the
CPU speed.

OTOH, my machine may be faster than yours (Intel Core 2 >= 2.0 Ghz).

-- 
  .''`.  Aurelien Jarno	            | GPG: 1024D/F1BCDB73
 : :' :  Debian developer           | Electrical Engineer
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