[Xen-users] ioremap failure on highmem reserved memory with RHEL 5 Xen Linux

["Girish Shirasat" <girish.shirasat@xxxxxxxxxxxxxx>]

Hello ,

    I have installed RHEL 5 on a Intel Core Duo processor based board. It has 1 GB of physical memory. I  have a driver which uses the memory reserved at the top of the high memory. Well this driver worked fine on all the previous versions of RHEL/FC and also with RHEL 5 with virtualization disabled. But  with virtualization enabled , the ioremap to the memory reserved at the top of high mem( usin highmem command line option) fails. On digging into the kernel code, I found out that the check if the memory address which I am passing to the ioremap is falling in the low memory region is failing. I rechecked if this is the case by printing the system information which confirmed that the address is not in the low mem. Also another thing which i noticed was that the high mem start which is normally set to 896MB is shifted to 728MB which confused me even further. Further looking into the ioremap code, the check is failing due to the fact that the mfn_to_local_pfn is giving a value which is less that max pfn . I was under the assumptions that the mfn should be equal for the pfn for Dom0.

Is there anything I need to do in the driver specific to Xen to access the reserved memory.I would really appreciate if anybody can help me out on this as I am new to Xen.

 

regards,

Girish

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