[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: [PATCH] x86: define arch_vm_get_page_prot to set _PAGE_IOMAP on VM_IO vmas
On 10/21/2010 04:17 PM, Jeremy Fitzhardinge wrote: > > Xen PV guests are always responsible for constructing ptes with machine > addresses in them (ie, doing their own pseudo-physical to machine > address conversion), and Xen verifies that the pages they want to map > either belong to them or have been granted to them. The _PAGE_IOMAP > flag is a kernel-internal one which allows us to distinguish between > ptes intended to map memory vs machine hardware addresses; it is not > part of the Xen ABI. > > If you're passing a device through to a domain, the domain is given > access to the device's address space so it can legally map those pages > (and if an IOMMU is available, the device is constrained to only DMA > that domain's memory). > Okay, could you clarify this part a bit? Why does the kernel need to know the difference between "pseudo-physical" and "machine addresses" at all? If they overlap, there is a problem, and if they don't overlap, it will be a 1:1 mapping anyway... -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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