Re: [PATCH v2 02/18] x86/sgx: Store struct sgx_encl when allocating new VA pages

[Dave Hansen]

On 12/2/22 13:40, Kristen Carlson Accardi wrote:
> On Fri, 2022-12-02 at 13:35 -0800, Dave Hansen wrote:
>> On 12/2/22 10:36, Kristen Carlson Accardi wrote:
>>> When allocating new Version Array (VA) pages, pass the struct
>>> sgx_encl
>>> of the enclave that is allocating the page. sgx_alloc_epc_page()
>>> will
>>> store this value in the encl_owner field of the struct
>>> sgx_epc_page. In
>>> a later patch, VA pages will be placed in an unreclaimable queue,
>>> and then when the cgroup max limit is reached and there are no more
>>> reclaimable pages and the enclave must be oom killed, all the
>>> VA pages associated with that enclave can be uncharged and freed.
>> What does this have to do with the 'encl' that is being passed,
>> though?
>>
>> In other words, why is this new sgx_epc_page-to-encl mapping needed
>> for
>> VA pages now, but it wasn't before?
> When we OOM kill an enclave, we want to get rid of all the associated
> VA pages too. Prior to this patch, there wasn't a way to easily get the
> VA pages associated with an enclave.

Given an enclave, we have encl->va_pages to look up all the VA pages.
Also, this patch's code allows you to go from a va page to an enclave.
That seems like it's going the other direction from what an OOM-kill
would need to do.