Re: [RFC] Randomness on confidential computing platforms

[Nikolay Borisov <nik.borisov@suse.com>]

On 26.01.24 г. 15:42 ч., Kirill A. Shutemov wrote:
> 4. Exit to the host/VMM with an error indication after a Confidential
>     Computing Guest failed to obtain random input from RDRAND/RDSEED
>     instructions after reasonable number of retries. This option allows
>     host/VMM to take some correction action for cases when the load on
>     RDRAND/RDSEED instructions has been put by another actor, i.e. the
>     other guest VM. The exit to host/VMM in such cases can be made
>     transparent for the Confidential Computing Guest in the TDX case with
>     the assistance of the TDX module component.

But is this really a viable solution in the face of malicious VMM? It 
assumes that if the VMM is signaled that randomness has been exhausted 
it will try to rectify it, what if such a signal can instead be 
repurposed for malicious purposes? Could it perhaps be used as some sort 
of a side channel attack ?