Re: [Qemu-devel] [PATCHv2] macio: handle non-block ATAPI DMA transfers the same as block DMA transfers

[Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>]

On 01/08/15 19:33, Aurelien Jarno wrote:

> On 2015-08-01 17:54, Mark Cave-Ayland wrote:
>> The existing code incorrectly changes the dma_active flag when a non-block
>> transfer has completed leading to a hang on newer versions of Linux because the
>> IDE and DMA engines deadlock waiting for each other.
>>
>> Instead copy the buffer directly to RAM, set the remaining transfer size to 0 and
>> then invoke the ATAPI callback manually once again to correctly finish the
>> transfer in an identical manner to a block transfer.
>>
>> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
>> ---
> 
> Thanks for the patch, it improves things here. I don't get messages
> anymore, and I get less messages when mounting the CD-ROM, though I
> still get one:
> 
>   [  307.258463] pata-macio 0.00021000:ata-4: timeout flushing DMA
>   [  307.262856] ata2.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
>   [  307.262919] ata2.00: BMDMA stat 0x6
>   [  307.263048] sr 1:0:0:0: CDB: Get configuration: 46 00 00 28 00 00 00 00 10 00
>   [  307.263289] ata2.00: cmd a0/01:00:00:10:00/00:00:00:00:00/a0 tag 0 dma 16400 in
>   [  307.263297]          res 41/50:03:00:10:00/00:00:00:00:00/a0 Emask 0x20 (host bus error)
>   [  307.263407] ata2.00: status: { DRDY ERR }
>   [  307.271251] ata2.00: configured for MWDMA2
>   [  307.271824] ata2: EH complete
> 
> The CD-ROM is fully functional though.

Hmmmm yes I can recreate that here - must be another transition between
the non-block and the block transfer code (I was working on eliminating
the boot messages) caused by reading the disc metadata upon mount.
Unfortunately I don't have much time to work on this right now so maybe
it's a 2.4.1/2.5 thing unless John can take a look?


ATB,

Mark.