Re: [RFC PATCH v3 0/6] Direct Map Removal for guest_memfd

[Patrick Roy]

On Fri, 2024-11-15 at 17:10 +0000, David Hildenbrand wrote:
>> [...]
>>
>> I've talked to Fares internally, and it seems that generally doing
>> mm-local mappings of guest memory would work for us. We also figured out
>> what the "interrupt problem" is, namely that if we receive an interrupt
>> while executing in a context that has mm-local mappings available, those
>> mappings will continue to be available while the interrupt is being
>> handled.
> 
> Isn't that likely also the case with secretmem where we removed the
> directmap, but have an effective per-mm mapping in the (user-space
> portion) of the page table?

Mh, that's an excellent point, I never thought of that. But with
secretmem, the memory would still be protected by SMAP (admittedly, I
have no idea how much this is worth in the face of all these speculative
issues), right?

>> I'm talking to my security folks to see how much of a concern
>> this is for the speculation hardening we're trying to achieve. Will keep
>> you in the loop there :)
> 
> Thanks!
> 
> -- 
> Cheers,
> 
> David / dhildenb

Best,
Patrick