RE: [Xen-devel] real-mode switch

["Jayant Mangalampalli" <Jayant_Mangalampalli@xxxxxxxxxxx>]

Hmmm ... I am trying to add this code to the hypervisor since currently
I am not aware of such support in xen. Is there a hypercall support to
switch between real- and protected modes already?

Thanks
Jayant

 

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Jayant Mangalampalli
> Sent: 05 June 2007 14:19
> To: ron minnich; xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-devel] real-mode switch
> 
> I am trying to switch to real-mode to make some BIOS calls. 
> However, when I try to remap kernel at virtual address 0 I 
> get "Unable to handle kernel paging request at virtual 
> address c06e0000" error. Here is where I get it:
> 
> memcpy(swapper_pg_dir, swapper_pg_dir + USER_PGD_PTRS, 
> sizeof(swapper_pg_dir[0]) * KERNEL_PGD_PTRS);

You can't remap the kernel to 0 - you'll have to use the Hypervisor if
you want to get to real-mode, I think. There was some talk about making
a hypercall to "call this bit of code as real-mode". 

--
Mats
> 
> swapper_pg_dir is 0xc06e0000, and user PGD pointers start at 
> 0x400 and kernel pointers start at 0x100. Any idea why I get this?
> 
> Thanks,
> 
> Jayant Mangalampalli
> 
> 



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