Re: problem about dma

["Gleb O. Raiko" <raiko@niisi.msk.ru>]

wuming wrote:
> Before the dma transfer, pci_map_sg will map the memory space covered by 
> sg_table,
> and it will flush and invalidate cache indexed by that memory space.
> After the dma transfer, pci_unmap_sg also needs to be called to flush and 
> invalidate
> the same cache. But I do not know why the second flush will be demanded.
> I think that in the interval between the two flush, there would be nothing to 
> access
> the memory covered by the dma. But it is not the case.
> I want to know what can access that memory and I need some help.
In 2.4, memcpy's prefetch may (and, in practice, do, no smiles, it cost 
me a lot of time to realize) access that memory. I though it has been 
fixed in 2.6 someday.
Regards,
Gleb.