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

["Jayaraman, Bhaskar" <Bhaskar.Jayaraman@xxxxxxx>]

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.
>
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> http://lists.xensource.com/xen-devel



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