I already added these notes to the bug report; just wondering if anyone on
the mailing list can tell me what the check I commented out is trying to
protect from happening, how important it is, and why it fails under xen, and
how it can be worked around correctly:
I found the cause, and a work around that seems to do the job very well for
me, however I am completely unsure of the negative implications of what I've
done.
I'm sure someones computer would get up and make a trip to taco bell in the
early AM if they did this on their computer. This is a definate case of a
little bit of knowledge is a very dangerous thing.
I noticed the message in /var/log/dmesg that read:
"architecture does not support 28bit PCI busmaster DMA"
when booting with the xen kernel.
I downloaded and installed the kernel source RPM and tracked the message
down to /usr/src/linux/sound/pci/maestro3.c
I ended up changing the lines that read:
/* check, if we can restrict PCI DMA transfers to 28 bits */
if (pci_set_dma_mask(pci, 0x0fffffff) < 0 ||
pci_set_consistent_dma_mask(pci, 0x0fffffff) < 0) {
snd_printk(KERN_ERR "architecture does not support 28bit PCI
busmaster DMA\n");
pci_disable_device(pci);
return -ENXIO;
}
to read like this (commented out the printk, pci disable and return):
/* check, if we can restrict PCI DMA transfers to 28 bits */
if (pci_set_dma_mask(pci, 0x0fffffff) < 0 ||
pci_set_consistent_dma_mask(pci, 0x0fffffff) < 0) {
//snd_printk(KERN_ERR "architecture does not support 28bit
PCI busmaster DMA\n");
//pci_disable_device(pci);
//return -ENXIO;
}
From there I compiled the module and replaced the existing snd-maestro3.ko
in /lib/modules/2.6.15-1.2032_FC5xen0/kernel/sound/pci and rebooted to
reload all the sound modules and now I have good working sound, with no
obvious ill effects.
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