Re: port-cats/18026 cats fails to dump kernel core

[Robert Swindells <rjs%fdy2.demon.co.uk@localhost>]

Chris Gilbert wrote:
>Chris Gilbert wrote:
>> Hi,
>> 
>> Just thought I'd let people know I've managed to dig into this one a bit.
>> 
>> The issue looks to be related to the memory map in some way.  When doing
>> the memory dump cats use DMA to do the transfers, having enabled dma
>> debugging and some pciide debugging, it seems that the hang probably
>> isn't a bug in the dma code, but something else.
>> 
>> Basically when the code attempts to dump the memory page at 0xB8000 the
>> system hangs.   It doesn't matter how big the DMAs are, if it's the
>> first page that we attempted to dump, it always hangs.
>> 
>> Searching google seems to show that 0xb8000 is a common address for vga
>> on x86.  I'm wondering if the M1543 chip has decided that address is
>> special (as it's a x86 southbridge) and gets itself confused, and hangs
>> the system.

>Having done more digging into this issue, the range of effected
>addresses is 0xb8000-0xc0000.  Searching this is a common vga range.

>My best guess as to the cause of the hangs is that the vga card has
>decided to respond to those addresses on the pci bus, and so the IDE DMA
> gets confused.

[snip]

I wonder whether this is caused by the video BIOS code being called by
the boot firmware.

Robert Swindells