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xen-devel
Re: [Xen-devel] passing hypercall parameters by pointer
On 19 Aug 2005, at 12:52, Jimi Xenidis wrote:
IP> Since passing by VA is so convenient on the architectures that
IP> support it we may not want to do anything different on these
IP> anyhow.
I agree, why create a new mapping when a usable one exists.
At least for common kernel code, we will need to wrap such VAs in a
macro so that the "psuedo-physical" is passed in for PPC. I assume
this is reasonable?
This is all potentially fixable before 3.0 final. Paravirt x86 can
continue to use guest virtual addresses. The idea would be that the
registration scheme would essentially create a parameter-passing
'address space' into which you hook pages of memory. On x86 we would
map the address space onto regions of kernel va space. On other arches
we would map the address space onto physical addresses that get mapped
into Xen's va space. get_user/put_user/copy_from_user/copy_to_user will
take guest addresses that point into this parameter-passing address
space.
At least we can scope it out by doing a few hypercalls to start with --
probably dom0_ops first and see how it pans out. I think it will work
quite well...
-- Keir
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