[Xen-devel] Re: [PATCH] x86: define arch_vm_get_page_prot to set _PAGE_IOMAP on VM_IO vmas

["H. Peter Anvin" <hpa@xxxxxxxxx>]

On 10/21/2010 03:40 PM, Jeremy Fitzhardinge wrote:
> 
> Set _PAGE_IOMAP in ptes mapping a VM_IO vma.  This says that the mapping
> is of a real piece of physical hardware, and not just system memory.
> 
> Xen, in particular, uses to this to inhibit the normal pfn->mfn conversion
> that would normally happen - in other words, treat the address directly
> as a machine physical address without converting it from pseudo-physical.
> 
> [ Impact: make VM_IO mappings map the right thing under Xen ]
> 
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> 

Am I the only one who thinks this seems extremely odd that the guest is
trusted to make this distinction?

        -hpa

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