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Re: kern/45671: Current NetBSD/i386 does not install under current qemu
The following reply was made to PR kern/45671; it has been noted by GNATS.
From: Andreas Gustafsson <gson%gson.org@localhost>
Cc: Jukka Ruohonen <jruohonen%iki.fi@localhost>, David Young
Subject: Re: kern/45671: Current NetBSD/i386 does not install under current qemu
Date: Wed, 11 Jan 2012 19:08:55 +0200
I found the cause of this; thanks to Jukka Ruohonen and David Young
for pointing me in the right direction.
Qemu broke the emulation of the PCI configuration register at I/O port
0xCF8, such that doing an outb to port 0xCFB or an outw to port 0xCFA
now changes the value of the configuration register. Because no real
PCI configuration register behaves that way, NetBSD concludes that the
emulated system doesn't support PCI configuration mode 1 and assumes
it must therefore support configuration mode 2. It then panics when
it finds a PCI device with device number 16, because mode 2 only
supports 4-bit device numbers.
There is a simple patch to qemu which has been verified to fix the
but at the time of writing, it has not yet been applied to the qemu
Even though this is clearly a qemu bug, there is probably still
some room for improvement on the NetBSD side in terms of failing
more gracefully and/or providing better diagnostics.
Andreas Gustafsson, gson%gson.org@localhost
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