Messages in this thread | | | Date | Sun, 07 Feb 2010 12:52:44 +0200 | From | Avi Kivity <> | Subject | Re: [PATCH 02/11] iommu-api: Add iommu_map and iommu_unmap functions |
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On 02/07/2010 12:50 PM, Joerg Roedel wrote: > On Sun, Feb 07, 2010 at 11:38:30AM +0200, Avi Kivity wrote: > >> On 01/28/2010 01:37 PM, Joerg Roedel wrote: >> >>> These two functions provide support for mapping and >>> unmapping physical addresses to io virtual addresses. The >>> difference to the iommu_(un)map_range() is that the new >>> functions take a gfp_order parameter instead of a size. This >>> allows the IOMMU backend implementations to detect easier if >>> a given range can be mapped by larger page sizes. >>> These new functions should replace the old ones in the long >>> term. >>> >>> >> These seem to be less flexible in the long term. Sure, it is easier for >> the backend to map to multiple page sizes if your iommu supports >> arbitrary power-of-two page sizes, but we should make the APIs easier >> for the callers, not the backend. >> > These functions are as flexible as the old ones which just tok a size. > The benefit of the new interface is that is makes the ability of the > IOMMU to map the area with a large page (an get the benefit of fewer > hardware tlb walks) visible to the caller. With the old interface the > caller is tempted to just map ist whole area using 4kb page sizes. > It gives a bit more complexity to the caller, thats right. But given > that the page allocator in Linux always returns pages which are aligned > to its size takes a lot of that complexity away. > >
You are right - I was thinking of the kvm use case which is range oriented, but the ordinary kernel interfaces are gfp_order oriented.
-- error compiling committee.c: too many arguments to function
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