HVMOP_altp2m_vcpu_enable_notify code example usage

HVMOP_altp2m_vcpu_enable_notify code example usage

[Dmitry Rockosov]

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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

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Re: HVMOP_altp2m_vcpu_enable_notify code example usage

[Tamas K Lengyel]

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@gmail.com> 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@lists.xen.org
> https://lists.xen.org/xen-devel
>

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Re: HVMOP_altp2m_vcpu_enable_notify code example usage

[Dmitry Rockosov]

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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?

Best Regards,
Rockosov Dmitry

2016-08-21 20:27 GMT+03:00 Tamas K Lengyel <tamas.k.lengyel@gmail.com>:

> 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@gmail.com>
> 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@lists.xen.org
> > https://lists.xen.org/xen-devel
> >
>

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Re: HVMOP_altp2m_vcpu_enable_notify code example usage

[Dmitry Rockosov]

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The problem is in hypervisor checking definitely. I deeper debugged the
code, I met vmcall instruction execution. This means EFAULT is coming from
hypervisor.

Best Regards,
Rockosov Dmitry

2016-08-22 18:09 GMT+03:00 Dmitry Rockosov <rockosov@gmail.com>:

> 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?
>
> Best Regards,
> Rockosov Dmitry
>
> 2016-08-21 20:27 GMT+03:00 Tamas K Lengyel <tamas.k.lengyel@gmail.com>:
>
>> 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@gmail.com>
>> 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@lists.xen.org
>> > https://lists.xen.org/xen-devel
>> >
>>
>
>

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Re: HVMOP_altp2m_vcpu_enable_notify code example usage

[Tamas K Lengyel]

On Mon, Aug 22, 2016 at 12:12 PM, Dmitry Rockosov <rockosov@gmail.com> 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@gmail.com>:
>>
>> 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@gmail.com>:
>>>
>>> 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@gmail.com>
>>> 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@lists.xen.org
>>> > https://lists.xen.org/xen-devel
>>> >
>>
>>
>

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Re: HVMOP_altp2m_vcpu_enable_notify code example usage

[Dmitry Rockosov]

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Tamas, what do you think, why the same hypercall operations (get_param) are
executed by Xen differently? Does Xen know anything about caller domU CPL:
usermode or kernelmode?

Thank you for answers!

Best Regards,
Rockosov Dmitry

2016-08-22 21:28 GMT+03:00 Tamas K Lengyel <tamas.k.lengyel@gmail.com>:

> On Mon, Aug 22, 2016 at 12:12 PM, Dmitry Rockosov <rockosov@gmail.com>
> 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@gmail.com>:
> >>
> >> 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@gmail.com>:
> >>>
> >>> 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@gmail.com>
> >>> 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@lists.xen.org
> >>> > https://lists.xen.org/xen-devel
> >>> >
> >>
> >>
> >
>

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Re: HVMOP_altp2m_vcpu_enable_notify code example usage

[Tamas K Lengyel]

On Mon, Aug 22, 2016 at 12:42 PM, Dmitry Rockosov <rockosov@gmail.com> wrote:
> Tamas, what do you think, why the same hypercall operations (get_param) are
> executed by Xen differently? Does Xen know anything about caller domU CPL:
> usermode or kernelmode?

It's not about the guest's CPL - all hypercalls are issued ultimately
from kernelmode anyway - but depending on which HVMOP the guest issues
it can get treated differently by Xen. You can follow the path from
here: https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/arch/x86/hvm/hvm.c;h=0180f26b56b75c08c8c53b58a599de6085949bce;hb=HEAD#l5510.
I'm not sure which HVMOPs are allowed by default to be executed by the
guest itself.

Tamas

>
> Thank you for answers!
>
> Best Regards,
> Rockosov Dmitry
>
> 2016-08-22 21:28 GMT+03:00 Tamas K Lengyel <tamas.k.lengyel@gmail.com>:
>>
>> On Mon, Aug 22, 2016 at 12:12 PM, Dmitry Rockosov <rockosov@gmail.com>
>> 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@gmail.com>:
>> >>
>> >> 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@gmail.com>:
>> >>>
>> >>> 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@gmail.com>
>> >>> 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@lists.xen.org
>> >>> > https://lists.xen.org/xen-devel
>> >>> >
>> >>
>> >>
>> >
>
>

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Re: HVMOP_altp2m_vcpu_enable_notify code example usage

[Dmitry Rockosov]

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Tamas,

My experiment is using the same HVMOP - HVMOP_get_param.
Usermode code is using it from
https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/include/public/hvm/hvm_op.h;hb=2a99aa99fc84a45f505f84802af56b006d14c52e
Kernelmode is using it from
http://lxr.free-electrons.com/source/include/xen/interface/hvm/hvm_op.h?v=3.16#L27

One difference I see, in usermode we are allocating buffer with
DECLARE_HYPERCALL_BUFFER in CPL3 space, in kernelmode it's made in CPL0
space, however privcmd IOCTL handler does copy_from_user call for argument
buffer... I'm very confused, why it happens :-(

Best Regards,
Rockosov Dmitry

2016-08-22 21:54 GMT+03:00 Tamas K Lengyel <tamas.k.lengyel@gmail.com>:

> On Mon, Aug 22, 2016 at 12:42 PM, Dmitry Rockosov <rockosov@gmail.com>
> wrote:
> > Tamas, what do you think, why the same hypercall operations (get_param)
> are
> > executed by Xen differently? Does Xen know anything about caller domU
> CPL:
> > usermode or kernelmode?
>
> It's not about the guest's CPL - all hypercalls are issued ultimately
> from kernelmode anyway - but depending on which HVMOP the guest issues
> it can get treated differently by Xen. You can follow the path from
> here: https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=
> xen/arch/x86/hvm/hvm.c;h=0180f26b56b75c08c8c53b58a599de
> 6085949bce;hb=HEAD#l5510.
> I'm not sure which HVMOPs are allowed by default to be executed by the
> guest itself.
>
> Tamas
>
> >
> > Thank you for answers!
> >
> > Best Regards,
> > Rockosov Dmitry
> >
> > 2016-08-22 21:28 GMT+03:00 Tamas K Lengyel <tamas.k.lengyel@gmail.com>:
> >>
> >> On Mon, Aug 22, 2016 at 12:12 PM, Dmitry Rockosov <rockosov@gmail.com>
> >> 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@gmail.com>:
> >> >>
> >> >> 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@gmail.com>:
> >> >>>
> >> >>> 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@gmail.com>
> >> >>> 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@lists.xen.org
> >> >>> > https://lists.xen.org/xen-devel
> >> >>> >
> >> >>
> >> >>
> >> >
> >
> >
>

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