Re: [Xen-devel] Get IDT from virtual machine

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

The IDT isn't even necessarily expressible as a PV 'trap_table': e.g., task
gates can't be expressed, nor can the interrupt-stack selector bits in a
64-bit gate.

 -- Keir

On 4/2/08 13:28, "Matthew Donovan" <matthew@xxxxxxxxxxxxxx> wrote:

> I'm sorry if I wasn't clear.  I was wondering why xc_vcpu_getcontext doesn't
> get the IDT for HVM guests and what would be required to make it work.
> 
> -matthew
> 
> -----Original Message-----
> From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx]
> Sent: Saturday, February 02, 2008 5:19 AM
> To: Matthew Donovan; xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Get IDT from virtual machine
> 
> Yes, your code extracts the virtual IDT for a PV guest. As I said below,
> doing it for an HVM guest requires you to issue a hvm-save-state hypercall
> and then pick apart the binary structure that is returned.
> 
>  -- Keir
> 
> 
> On 1/2/08 17:20, "Matthew Donovan" <matthew@xxxxxxxxxxxxxx> wrote:
> 
>>  But one could get the IDTR for a para-virt guest?  Out of curiousity,
>> how hard would it be to do it for HVM guests?
>> 
>> -matthew
>> 
>> -----Original Message-----
>> From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx]
>> Sent: Friday, February 01, 2008 3:40 AM
>> To: Matthew Donovan; xen-devel@xxxxxxxxxxxxxxxxxxx
>> Subject: Re: [Xen-devel] Get IDT from virtual machine
>> 
>> That's very wishful code! Unfortunately the IDTR is not exposed via
>> vcpu_context for HVM guests. The only way to get it right now is to do
>> a hvm save hypercall and then parse the pickled state to find the
>> IDTR. It actually should be quite easy.
>> 
>>  -- Keir
>> 
>> On 31/1/08 21:31, "Matthew Donovan" <matthew@xxxxxxxxxxxxxx> wrote:
>> 
>>> 
>>> I'm trying to retrieve and print the interrupt descriptor table of a
>>> guest OS but every address is coming out 0x00000000.
>>> 
>>> Here's what I'm doing:
>>> 
>>>     vcpu_guest_context_t ctx;
>>>     int i;
>>> 
>>>     int res = xc_vcpu_getcontext (xai->xc_handle, xai->domain_id, 0,
>> &ctx);
>>>     if (res < 0) {
>>>         fprintf (stderr, "xc_vcpu_getcontext failed!\n");
>>>         return;
>>>     }   
>>> 
>>>     for (i = 0 ; i < 256 ; ++i) {
>>>         printf ("Interrupt %d: Address 0x%08x\n",
>>>                 i,
>>>                 ctx.trap_ctxt[i].address);
>>>     }
>>> 
>>> 
>>> I'm using Xen 3.1.2 on Fedora Core 8.  The guest OS's have been XP
>>> Pro and Vista Ultimate, though I assume that part doesn't matter
>>> since the IDT is a processor structure.
>>> 
>>> Any help is greatly appreciated.
>>> -matthew
>>> 
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>>> http://lists.xensource.com/xen-devel
>> 
>> 
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-devel
> 



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