Messages in this thread | | | Date | Thu, 20 Nov 2014 12:21:23 +0100 | From | "Jan Beulich" <> | Subject | Re: [Xen-devel] [PATCH 4/4] x86/xen: use the maximum MFN to calculate the required DMA mask |
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>>> On 19.11.14 at 17:02, <david.vrabel@citrix.com> wrote: > On a Xen PV guest the DMA addresses and physical addresses are not 1:1 > (such as Xen PV guests) and the generic dma_get_required_mask() does > not return the correct mask (since it uses max_pfn). > > Some device drivers (such as mptsas, mpt2sas) use > dma_get_required_mask() to set the device's DMA mask to allow them to > use only 32-bit DMA addresses in hardware structures. This results in > unnecessary use of the SWIOTLB if DMA addresses are more than 32-bits, > impacting performance significantly. > > Provide a get_required_mask op that uses the maximum MFN to calculate > the DMA mask. > > Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
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