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


From: Aurelien Jarno
Subject: Re: [Qemu-devel] [PATCH] MIPS: Fix dmtc0 instruction
Date: Tue, 26 Aug 2008 00:26:21 +0200
User-agent: Mutt/1.5.18 (2008-05-17)

On Mon, Aug 25, 2008 at 11:10:32PM +0200, Thiemo Seufer wrote:
> Stefan Weil wrote:
> > Thiemo Seufer schrieb:
> > > 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.
> > >
> > >
> > > Thiemo
> > There is a problem with the current count/compare emulation:
> > c0_compare_int_usable in newer Linux kernels fails to detect that it is
> > usable.
> > 
> > I had a Mips Linux kernel hanging while calibrating bogo mips caused by
> > this.
> > A workaround was running Qemu with all debug output enabled (-d ...),
> > so a slower running Qemu was better.
> > 
> > A crude workaround is here:
> > http://svn.berlios.de/svnroot/repos/ar7-firmware/qemu/trunk/hw/mips_timer.c
> > 
> > I don't really like my patch, but it improves count/compare emulation, and
> > my kernel no longer hangs when running in Qemu. Maybe you can try it
> > with your kernel.
> 
> No change with my testcase (which is available from
> http://people.debian.org/~ths/qemu/lenny64/).
> 

I have just tried on my computer. I confirm it work fine without any
specific patches.

Aurelien

-- 
  .''`.  Aurelien Jarno             | GPG: 1024D/F1BCDB73
 : :' :  Debian developer           | Electrical Engineer
 `. `'   address@hidden         | address@hidden
   `-    people.debian.org/~aurel32 | www.aurel32.net




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