[Xen-devel] Bug with xc_translate_foreign_address?

["Lewis, Christopher S." <Christopher.Lewis@xxxxxxxxxx>]

Hi all,

 

I am receiving an error on a VT HVM, which appears to be located in the function xc_translate_foreign_address.

 

Running the xenctx tool on a VT HVM (xen-testing 3.0.2) it returns:

 

# ./xenctx -f 1
eip: c027b646
esp: c0441ed4
eax: 000000c4   ebx: c0495300   ecx: 000001f7   edx: 000001f7
esi: c0495394   edi: 00000000   ebp: c027fec0
 cs: 00000060    ds: 0000007b    fs: 00000000    gs: 00000033

 

Stack:
failed to map PT
failed to map page.

 

Upon inspection, the value of cr3 in xc_translate_foreign_address (after the line cr3 = ctx.ctrlreg[3]) is set to be 0 if the xenctx tool is run immediately after the system is booted and a domU is created.  However, if I wait until after I see the second "(XEN) HVM_PIT: guest freq in cycles="<some value> in the xen dmesg, the value of cr3 is then set to a value. However, the error shown above remains the same.

 

Running the same command on a non-VT machine (32bit non-PAE)  (xen-testing 3.0.2) it returns:

 

# ./xenctx -f 1
eip: b7e4a547
esp: bfc26164
eax: 080f6968   ebx: b7bdcff4   ecx: b7f16ff4   edx: 080f6968
esi: b7dec6a0   edi: 00000000   ebp: bfc26164
 cs: 00000073    ds: 0000007b    fs: 00000000    gs: 00000033

 

Stack:
 bfc26184 b7bd8551 080f6968 b7bdbb2d bfc2618c b7bdcff4 b7dec6a0 b7f19098
......
etc.

 

Cr3 is immediately set on this machine and the xenctx command completes successfully.

 

It appears that this stems from a problem of mapping the CR3 register to the mfn on the VT  HVM -- this operation successfully completes on the non-VT machine, however, it doesn't resolve correctly for VT HVM.

 

Does anyone else have this issue?

 

Thanks,
~Chris

 

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