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Re: [Qemu-devel] enabling bus-master IDE driver

From: Jason Brittain
Subject: Re: [Qemu-devel] enabling bus-master IDE driver
Date: Fri, 05 Nov 2004 17:53:01 -0800
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20040913

zitu wrote:
Quoting zitu <address@hidden>:

Does that mean that the patch doesn't work?  Do I have to do something else
to make dma work?

I think this patch is almost complete for linux and solaris guests. Some
more work/init is needed inside XP/NT/2K. Anyone around with this
knowledge ?

answering to myself... :)

WIN_WRITEDMA_EXT & WIN_READDMA_EXT cases are not defined in hw/ide.c
I have no idea where to start to write a patch for these... :(

Until these and the atapi_dma are set/defined, no dma should work IMHO.
And this seems not to be OS dependant.

Which means the linux figures I got were wrong ???

My Linux (kernel 2.6) guest's disk seems slow too.  I applied the DMA
patch, and at first it seemed faster (it may be a bit faster).  But,
I tried using hdparm -d1 /dev/hda to make sure DMA was turned on in
the guest Linux and it said:

 setting using_dma to 1 (on)
 HDIO_SET_DMA failed: Operation not permitted
 using_dma    =  0 (off)

So I'm pretty sure DMA doesn't work with this patch even with a Linux
guest -- at least in my setup.

Jason Brittain

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