[Xen-devel] xen-swiotlb and linux swiotlb

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Hi Konrad,

Don't know if this is logical, since it uses the same range.

[    0.000000] Placing 64MB software IO TLB between ffff880003d00000 - 
ffff880007d00000
[    0.000000] software IO TLB at phys 0x3d00000 - 0x7d00000

[    0.047391] PCI-DMA: Using software bounce buffering for IO (SWIOTLB)
[    0.047402] Placing 64MB software IO TLB between ffff880003d00000 - 
ffff880007d00000
[    0.047406] software IO TLB at phys 0x3d00000 - 0x7d00000


And with 2.6.36pre:

[    0.000000] DMA: Placing 64MB software IO TLB between ffff88000eb5d000 - 
ffff880012b5d000
[    0.000000] DMA: software IO TLB at phys 0xeb5d000 - 0x12b5d000
[    0.000000] xen_swiotlb_fixup: buf=ffff88000eb5d000 size=67108864
[    0.000000] xen_swiotlb_fixup: buf=ffff880012bbd000 size=32768

[    3.297348] DMA-API: preallocated 32768 debug entries
[    3.300022] DMA-API: debugging enabled by kernel config
[    3.300022] PCI-DMA: Using software bounce buffering for IO (SWIOTLB)
[    3.300022] DMA: Placing 64MB software IO TLB between ffff88000eb5d000 - 
ffff880012b5d000
[    3.300022] DMA: software IO TLB at phys 0xeb5d000 - 0x12b5d000


Seems xen-swiotlb splits the mem space, and the 32768 is probably for a 
translaction table ?
Since it gets overriden by the normal swiotlb later on, this mem could be used 
by devices as DMA mem, and since it is on the end, it could take a while ..  
and finally overwrite mem it shouldn't and freeze everyting ?

--
Sander


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