Re: [Qemu-devel] qemu and solaris, suggested pci-ide DMA PATCH

["Bochnig, Martin" <mb1x@gmx.com>]

Hi,

very good,
thanx.

I will try it tonight.


Martin


Juergen Keil wrote:
> I wrote:
> 
> 
>>As far as I understand it, the Solaris ata driver does not use DMA
>>transfers with the "pci-ide" qemu hardware, because the "bus master
>>support indicator" bit in pci configuration space offset 09h is not
>>set.
>>
>>The message from the Solaris 10 b63 kernel is something like:
>>
>>  "ATA DMA off: cntrl not Bus Master DMA capable"
>>
>>So it'll fall back to PIO mode transfers.  PIO transfers may be slow, but
>>that's OK, so far.
> 
> 
> The following patch changes the qemu pci-ide device to report a
> "pci buster master ide controller" instead of a "pci ide controller
> (without bus master support)".  With that patch installed, a Solaris x86
> guest os starts using DMA ide transfers.  Maximum transfer rates on the qemu
> ide hdd doubles (I observe ~10MByte/sec in DMA mode vs. ~5MByte/sec in PIO
> mode). 
> 
> (The patch includes the busmaster status register patch I send two days ago,
> to enable the pci-ide controller for Solaris x86 in qemu "-pci" mode)