Re: [Xen-devel] Checking hypercall page existence!

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

Dumping the page contents and disassembling would be sensible.

 -- Keir

On 2/11/08 07:28, "Jayaraman, Bhaskar" <Bhaskar.Jayaraman@xxxxxxx> wrote:

> No Keir, VxWorks doesn't have a user, kernel context and everything runs in
> kernel mode in it. All tasks are scheduled in Ring0 on it so I'm not entirely
> sure why my hypercalls are failing, although I'm able to load the hypercall
> page. I'll try invoking a few more calls and check if all the hypercalls are
> failing. I'm hoping that if I call more hypercalls and if the hypercall page
> hasn't even loaded properly maybe I'm missing an instruction segment interrupt
> (Invalid opcode etc) as the hypercall branch is probably going to a legitimate
> instruction address for the ones I'm calling right now.
> On the other hand I was also thinking of dumping the whole 4k page laoded by
> wrmsr onto the terminal and check for hypercall opcodes within it to see if
> the page was actually loaded. If there's some other way of checking if the
> page has loaded properly, or if you think I may have to do something else to
> make the calls work please let me know.
> Bhaskar.
> ________________________________________
> From: Keir Fraser [keir.fraser@xxxxxxxxxxxxx]
> Sent: Saturday, November 01, 2008 4:40 AM
> To: Jayaraman, Bhaskar; xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Checking hypercall page existence!
> 
> You can only execute hypercalls from ring 0 (kernel context), not user
> space. Is that your problem?
> 
>  -- Keir
> 
> On 1/11/08 08:15, "Jayaraman, Bhaskar" <Bhaskar.Jayaraman@xxxxxxx> wrote:
> 
>> Hi, I've mapped hypercall pages onto a VxWorks HVM using the CPUID and WRMSR
>> instructions on a 32 bit pentium machine. However, when I'm trying to make a
>> hypercall on it the hypercall on it I'm unable to succeed and it fails. I
>> tried the HYPERVISOR_xen_version and HYPERVISOR_vm_assist hypercalls and they
>> both are returning < 0 values.
>> I was wondering whether there is any way in which I can verify whether the
>> hypercall pages have actually been mapped. I could take a dump of the pages
>> that wrmsr maps into my domain and look through it for hypercall opcodes but
>> if there is an easier way to confirm that, like a signature in the page
>> mapped, please let me know.
>> Thanks.
>> Bhaskar.
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-devel
> 
> 



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