RE: [Xen-ia64-devel] Strange problem with virtual aliases

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

Hi,

Matthew Chapman write on 2006年11月29日 16:13:
> Hi folks,
> 
> I have a curious Xen/ia64 problem which looks like it could be a bug.
> 
> I'm running my own small OS in DomU.  I've created two mappings which
> are supposed to be aliases; one is a large identity mapping, pinned
> through a translation register, the other maps a specific page:
> 
> itr.d dtr[r0]: 0x2000000000000000 -> 0 size 256M
>          (thus 0x2000000002500000 -> 0x2500000)
>         itc.d: 0x00000000fbdf7000 -> 0x2500000 size 4K


Did you access 0xfbdf7038 in guest physical mode?
Seems domU only support identity mapping in region 0.


Anthony.

> 
> tpa from inside the domain "proves" that the mappings are aliases:
> 
> tpa(0x2000000002500038) = 0x2500038
> tpa(0xfbdf7038) = 0x2500038
> 
> However reading the data shows they are not:
> 
> *(0x2000000002500038) = 0x2000000001
> *(0xfbdf7038) = 0
> 
> The real hardware TLB indeed has different physical addresses for the
> two pages:
> 
> #                     VA            PA     RID    KEY   PS MA  ATTR  
> PL PERMS 14 V A   00000000fbdf7000 0000017309000 000008 000000   4K
> WB  p a d     2 rwrwrw-- 69 V A   2000000002500000 0000017c00000
>                           010008 000000   4K WB  p a d     2 rwrwrw--
> ^^^^^^^^^^^^^ 
> 
> Before I spend more time delving through Xen, does anyone have any
> ideas 
> how this could have happened?
> 
> N.B. I've compiled Xen with 4KB page size which may or may not be
> relevant...  most likely not since Xenlinux runs fine.
> 
> Matt
> 
> 
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