Re: [PATCH v17 18/23] platform/x86: Intel SGX driver

[Dave Hansen]

On 12/17/18 11:55 AM, Andy Lutomirski wrote:
>> You're effectively rebuilding reverse-mapping infrastructure here.  It's
>> a frequent thing for the core VM to need to go from 'struct page' back
>> to the page tables mapping it.  For that we go (logically)
>> page->{anon_vma,mapping}->vma->vm_mm->pagetable.
> This is a bit outside my expertise here, but doesn't
> unmap_mapping_range() do exactly what SGX wants?

There's no 'struct page' for enclave memory as it stands.  That means no
page cache, and that means there's no 'struct address_space *mapping' in
the first place.

Basically, the choice was made a long time ago to have SGX's memory
management live outside the core VM.  I've waffled back and forth on it,
but I do still think this is the right way to do it.