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.leng...@gmail.com>:
> On Mon, Aug 22, 2016 at 12:12 PM, Dmitry Rockosov <rocko...@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 <rocko...@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.leng...@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 <rocko...@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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