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Re: [Xen-devel] [PATCH 0/6] grantable and address conversion patches

On 10 Apr 2006, at 10:34, Isaku Yamahata wrote:

4/6: Make the function that fills in map/unmap requests arch-specific?
At least filling in host_addr should be arch-specific -- we don't
really want to overload dev_bus_addr like this.

O.K. I'll introduce virt_to_host_addr() to xenLinux and make a new patch.
Is there any explanaition about host_addr and dev_bus_addr?
When I wrote this patch,I guessed that host_addr should have been
arch-indepedent and dev_bus_addr could be arch-depedent.
But it was wrong. I couldn't find any good explaination/usage samples
of these field.

Yes, the confusion is understandable. :-) The host_addr indicates where in the guest's address space the mapping should be placed --- on x86 this is either a virtual address or the address of a PTE to be updated with the mapping, but you can make it what you like and pseudo-phys address sounds like a good idea. The name 'host_addr' is pretty crappy, I'm not sure why it was chosen. 'guest_addr' would be more accurate.

How about defining a function in gnttab.c or gnttab.h to fill in an entire map/unmap structure, and make the filling of host_addr dependent on XENFEAT_auto_translated_physmap? I think we would do the same thing for VP guest on x86 (fill host_addr with pseudo-phys addr rather than virtual addr).

 -- Keir

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