Re: [XenPPC] Question? Re: [PATCH] Fix paddr_to_maddr panic message

[Hollis Blanchard]

On Thu, 2006-08-31 at 08:07 -0400, Jimi Xenidis wrote:
> 
> Hollis, ASAICT the only way Amos could have gotten here (and passed  
> the BUG() in pfn2mfn()) is if one of the user_copy routines tried to  
> access a PFN_TYPE_REMOTE or PFN_TYPE_IO, that paddr is not an IO type  
> so the question I have for you is:
>Is it possible for Xen (on behalf of a privileged domain) use a  
> user_copy routine to access another domains memory?

No. Because copy_*_guest() require a xencomm_desc structure to do
anything[1], they can only copy into areas of memory the domain expects.

However, if we need that functionality, we can create a parallel API to
do this. x86 does that right now with copy_*_user() -- that API only
exists in x86-specific code, and it directly accesses the "user" virtual
address.

[1] If we go with IA64's proposed "inline" extension to the xencomm
stuff, this isn't strictly true and I think we could copy to physically
contiguous areas that way.

-- 
Hollis Blanchard
IBM Linux Technology Center


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[XenPPC] Question? Re: [PATCH] Fix paddr_to_maddr panic message

[Jimi Xenidis]

On Aug 30, 2006, at 8:10 PM, [EMAIL PROTECTED] wrote:


I saw this fire once and was mightily confused by the "type" printed.


Thanks Amos, this pointed out a lot of INVALID_MFN cleanup that  
needed to be done, should push that soon.
Amos, IIRC the address that actually _was_ printed was was a paddr of  
0xc00 (192Mib), too bad thats all the inof we have :(


Hollis, ASAICT the only way Amos could have gotten here (and passed  
the BUG() in pfn2mfn()) is if one of the user_copy routines tried to  
access a PFN_TYPE_REMOTE or PFN_TYPE_IO, that paddr is not an IO type  
so the question I have for you is:
  Is it possible for Xen (on behalf of a privileged domain) use a  
user_copy routine to access another domains memory?


-JX




Signed-off-by: Amos Waterland <[EMAIL PROTECTED]>

---

 usercopy.c |4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff -r e12aa1195f58 xen/arch/powerpc/usercopy.c
--- a/xen/arch/powerpc/usercopy.c   Wed Aug 30 18:35:20 2006 -0400
+++ b/xen/arch/powerpc/usercopy.c   Wed Aug 30 20:08:35 2006 -0400
@@ -52,8 +52,8 @@ static unsigned long paddr_to_maddr(unsi
 case PFN_TYPE_LOGICAL:
 break;
 default:
-panic("%s: called with bad memory address type: 0x%lx\n",
-__func__, paddr);
+panic("%s: address 0x%lx has bad address type: 0x%x\n",
+__func__, paddr, mtype);
 break;
 }
 pa <<= PAGE_SHIFT;



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