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

[Thiemo Seufer]

Aurelien Jarno wrote:
> 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 address@hidden
> > [    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.

I'M not sure, I only inferred it is a timing problem from the printk timing
output.


Thiemo