[Barrelfish-users] About span domain and Vspace

孙思杰 sunsijie at buaa.edu.cn
Thu Jul 13 08:40:50 CEST 2017

Dear all,
I'm trying to run xmpl-span example over qemu.
It works on x86_64. but on armv7 reports a WRONG_CAP_TYPE error which is resulted from usr/monitor/monitor_server.c:827.
After I read all code about the span function, there is something about Vspace I don't quite understand.
1. After span a dispatcher on another core, the two dispatchers share the same pagetable but not the same vspace. The new dispatcher has a fresh vregion list and is not able to know which parts of virtual address space is already used. On armv7, it leads to allocating an allocated vaddr after first malloc and crash. It works on x86_64 because in function pmap_current_init, the min_mappable_va and META_DATA_RESERVED_BASE is changed according to core id. Does that mean that virtual address space is statically partitioned on x86_64?
2. On Barrelfish, everything between cores has to be replicated. Why new dispatch created by span function share the pagetable? Is it necessary to keep consistent between two dispatcher's vregion list. If it is, is there any mechanism to do so?

Sun SJ
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