[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] What's the purpose of VM_FOREIGN
VM_FOREIGN is used to allow zero-copy of data pages for the blktap driver. When foreign block data pages are mapped to user space, the PTEs aren't backed by page structs, so get_user_pages becomes upset when called to map the block requests down onto physical page addresses. VM_FOREIGN vm_areas use the vm_private_data field to contain an array of mappings to the associate page structs, and get_user_pages uses this table to handle pages that have been foreign mapped. The code that sets up the mapping is in drivers/xen/blktap.c. a. On 8/1/06, Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> wrote: > But I never saw when the bit is set, so this code path can not be > reached? > It's used by the blktap driver. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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