Re: [Xen-devel] [PATCH v3 1/2] x86/mm: Change default value for suppress #VE in set_mem_access()

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Thu, Jul 20, 2017 at 10:43 AM, George Dunlap
<George.Dunlap@xxxxxxxxxxxxx> wrote:
> On Wed, Jul 19, 2017 at 7:24 PM, Tamas K Lengyel <tamas@xxxxxxxxxxxxx> wrote:
>>> I think the issue would be whether to allow a domain to set/clear the
>>> suppress #VE bit for its pages by calling the new HVMOP on itself.
>>
>> This problem is not limited to setting the SVE bit. It also applies to
>> swapping altp2m views. Pretty much all altp2m HVMOPs can be issued
>> from a user-space program without any way to check whether that
>> process is allowed to do that or not. If you don't think it is safe
>> for a domain to set SVE, the none of the altp2m ops are safe for the
>> domain to issue on itself. If we could say ensure only the kernel can
>> issue the hvmops, that would be OK. But that's not possible at the
>> moment AFAICT.
>
> Wait, is that right?  I think we normally restrict hypercalls to only
> being made from the guest kernel, don't we?
>

If that's the case then it's good to know (can you point me where that
restriction is done?) I was just referring to the fact that
technically a userspace program can issue VMCALL.

Tamas

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