RE: [Xen-users] Possible problem with PAE?

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

 > I'm porting an OS to XEN 3.0 that uses PAE mode.
> It maps both virtual address space 0x00000000 and 0xC0000000 
> to the same physical address space, hence pgd slot 0 and pgd 
> slot 3 point to the same middle page directory. It appears 
> that XEN does not support this situation. The XEN error 
> message I get when I try to pin the pgd is
> 
> (XEN) DOM154: (file=mm.c, line=905) Failure in alloc_l3_table: entry 3
> (XEN) DOM154: (file=mm.c, line=1550) Error while validating 
> mfn d2a9 (pfn 10) for type 67ff0000: caf=80000003 taf=67ff0001
> (XEN) DOM154: (file=mm.c, line=1780) Error while pinning mfn d2a9
> 
> If I set pgd slot 0 to 0 the pin succeeds.
> 
> Does XEN support this "duplicate" mapping?

No. I imagine this is just in some start of day code in the OS that can
easily be re-jigged?

We have thought about supporting it as a slow-path operation, but it
would lead to greater complexity in the type checking code, so probably
not worth the effort.

> Is this the right place to ask this question?

xen-devel would be better.

BTW: what's the OS?

Best,
Ian

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