Re: [PATCH v1 4/7] x86/vmx: add do_vmtrace_op

[Michał Leszczyński <michal.leszczynski@xxxxxxx>]

----- 18 cze 2020 o 5:20, Tamas K Lengyel tamas.k.lengyel@xxxxxxxxx napisał(a):

>> >> +
>> >> +        a.mfn = v->arch.hvm.vmx.ipt_state->output_base >> PAGE_SHIFT;
>> >
>> > This will not work for translated domains, ie: a PVH or HVM domain
>> > won't be able to use this interface since it has no way to request the
>> > mapping of a specific mfn into it's physmap. I think we need to take
>> > this into account when deciding how the interface should be, so that
>> > we don't corner ourselves with a PV only interface.
>>
>> Please be aware that this is only going to be used by Dom0. Is is 
>> well-supported
>> case that somebody is using PVH/HVM Dom0?
>>
>> I think that all Virtual Machine Introspection stuff currently requires to 
>> have
>> Dom0 PV. Our main goal is to have this working well in combo with VMI.
> 
> FYI the VMI interface doesn't require a PV domain. It works fine from
> PVH dom0 or even from a secondary privileged HVM DomU as well,
> provided you have the right XSM policy to allow that.
> 
> Tamas


It was previously stated that:

> PVH or HVM domain
> won't be able to use this interface since it has no way to request the
> mapping of a specific mfn into it's physmap.

but however, taking LibVMI as an example:

https://github.com/libvmi/libvmi/blob/c461e20ae88bc62c08c27f50fcead23c27a30f9e/libvmi/driver/xen/xen.c#L51

An essential abstraction xen_get_memory() relies on xc_map_foreign_range(). 
Doesn't this mean that it's not usable from PVH or HVM domains, or did I got it 
all wrong?


Best regards,
Michał Leszczyński
CERT Polska