Re: [Xen-devel] HVMOP_altp2m_vcpu_enable_notify code example usage

[Tamas K Lengyel <tamas.k.lengyel@xxxxxxxxx>]

On Mon, Aug 22, 2016 at 12:12 PM, Dmitry Rockosov <rockosov@xxxxxxxxx> wrote:
> The problem is in hypervisor checking definitely. I deeper debugged the
> code, I met vmcall instruction execution. This means EFAULT is coming from
> hypervisor.

As it should, question is where exactly it gets denied in Xen.

>
> Best Regards,
> Rockosov Dmitry
>
> 2016-08-22 18:09 GMT+03:00 Dmitry Rockosov <rockosov@xxxxxxxxx>:
>>
>> Hello Tamas,
>>
>> Thank you for the answer!
>>
>> I installed the same xen source code (4.7.0) as on dom0 to domU, built
>> dist-tools, installed xen-tools, updated rc.d configuration and rebooted.
>> IOCTL channel to privcmd driver is working fine, but all requests to
>> hypervisor like hvm_get_param, translate_foreign_address,
>> altp2m_vcpu_enable_notify return EFAULT errno (Bad access).
>>
>> Just for experiment I wrote below code in usermode:
>> ===================================
>> ...
>> rc = xc_hvm_param_get(xch, DOMID_SELF, HVM_PARAM_CONSOLE_PFN, &value);
>> if (rc < 0) {
>>     PERROR("Fail to get CONSOLE PFN HVM PARAM\n");
>>     goto exit;
>> }
>> DPRINTF("CONSOLE PFN == %llx", (unsigned long long)value);
>> ...
>> ===================================
>>
>> and below code in kernelmode:
>> ===================================
>> ...
>> printk(KERN_INFO "We are in Xen domain HVM = %d\n", xen_hvm_domain());
>> err = hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &value);
>> printk(KERN_INFO "err = %d\n", err);
>> printk(KERN_INFO "CONSOLE PFN = %llx\n", value);
>> ...
>> ===================================
>>
>> In the usermode I got an error:
>> ===================================
>> Fail to get CONSOLE PFN HVM PARAM
>> : Bad address
>> ===================================
>>
>> In the kernelmode code executed fine:
>> ===================================
>> [23261.230188] We are in Xen domain HVM = 1
>> [23261.307840] err = 0
>> [23261.352587] CONSOLE PFN = fefff
>> ===================================
>>
>> Looks like usermode wrappers don't support many requests to hypervisor,
>> right?

Not sure about HVMOP_get_param but AFAIK for
HVMOP_altp2m_vcpu_enable_notify to work you would have to create the
domain with altp2mhvm=1 enabled, then also issue the required commands
from dom0 to enable it (xc_altp2m_set_domain_state) and also perhaps
create a couple altp2m views.

Tamas

>>
>> Best Regards,
>> Rockosov Dmitry
>>
>> 2016-08-21 20:27 GMT+03:00 Tamas K Lengyel <tamas.k.lengyel@xxxxxxxxx>:
>>>
>>> Hi Dmitry,
>>> as long as you are testing with a HVM Linux guest you should be able
>>> to just compile the Xen tools in the guest and then use libxc from
>>> within the guest to issue that hypercall via
>>> xc_altp2m_set_vcpu_enable_notify. You will need to load a couple Xen
>>> related kernel-modules for it to work (like xen-privcmd). Let us know
>>> if you got it working!
>>>
>>> Cheers,
>>> Tamas
>>>
>>> On Fri, Aug 19, 2016 at 1:19 PM, Dmitry Rockosov <rockosov@xxxxxxxxx>
>>> wrote:
>>> > Hello Xen Team!
>>> >
>>> > Does anybody have any code examples of HVMOP_altp2m_vcpu_enable_notify?
>>> >
>>> > I want to fully test #VE, VMFUNC and EPTP Switching VM Function 0 in
>>> > Xen,
>>> > but doesn't have any documentations/examples for it.
>>> > I tried xen-access test from tools/tests/xen-access, but looks like it
>>> > doesn't use VMFUNC and #VE, it simply changes VMCS entries with
>>> > vmwrite, w/o
>>> > VMFUNC 0 (EPTP Switching).
>>> >
>>> > Thanks in advance!
>>> >
>>> > Best Regards,
>>> > Rockosov Dmitry
>>> >
>>> > _______________________________________________
>>> > Xen-devel mailing list
>>> > Xen-devel@xxxxxxxxxxxxx
>>> > https://lists.xen.org/xen-devel
>>> >
>>
>>
>

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