Re: [PATCHv5 0/4] dma, x86, xen: reduce SWIOTLB usage in Xen guests

From: Greg Kroah-Hartman
Date: Fri Dec 05 2014 - 16:30:06 EST

On Fri, Dec 05, 2014 at 02:07:59PM +0000, David Vrabel wrote:
> On systems where DMA addresses and physical addresses are not 1:1
> (such as Xen PV guests), the generic dma_get_required_mask() will 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.
> This series allows Xen PV guests to override the default
> dma_get_required_mask() with a more suitable one.
> Changes in v5:
> - xen_swiotlb_get_required_mask() is x86 only.
> Changes in v4:
> - Assume 64-bit mask is required.
> Changes in v3:
> - fix off-by-one in xen_dma_get_required_mask()
> - split ia64 changes into separate patch.
> Changes in v2:
> - split x86 and xen changes into separate patches
> David

Why are you sending these to me? Am I the DMA maintainer and forgot
about it?

/me digs in MAINTAINERS...

Nope, not me! Patches are now deleted from my queue, go use
scripts/ like you should have done...

greg k-h
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