Re: [PATCH v2 0/2] x86/sgx: Limit EPC overcommit

[Jarkko Sakkinen <jarkko.sakkinen@iki.fi>]

On Fri, Jan 07, 2022 at 10:16:15AM -0800, Kristen Carlson Accardi wrote:
> SGX currently allows EPC pages to be overcommitted. If the system is
> out of enclave memory, EPC pages are swapped to normal RAM via
> a per enclave shared memory area. This shared memory is not charged
> to the enclave or the task mapping it, making it hard to account
> for using normal methods. Since SGX will allow EPC pages to be
> overcommitted without limits, enclaves can consume system memory
> for these backing pages without limits.
> 
> In order to prevent this, set a cap on the amount of overcommit SGX
> allows.  Whenever a backing page is requested by an enclave, track
> the total amount of shared memory pages used across all enclaves and
> return an error if the overcommit limit has been reached. This will
> restrict the total amount of backing pages that all enclaves can
> consume to a maximum amount, and prevent enclaves from consuming
> all the system RAM for backing pages.
> 
> The overcommit percentage has a value of 150, which limits shared
> memory page consumption to 1.5x the number of EPC pages in the system.
> 
> Changes from v1
> ----------------
> * removed module parameter and disable boolean
> * increased over commit percentage to 150% from 100%
> 
> Kristen Carlson Accardi (2):
>   x86/sgx: Add accounting for tracking overcommit
>   x86/sgx: account backing pages
> 
>  arch/x86/kernel/cpu/sgx/encl.c | 76 ++++++++++++++++++++++++++++++++--
>  arch/x86/kernel/cpu/sgx/encl.h |  6 ++-
>  arch/x86/kernel/cpu/sgx/main.c | 52 +++++++++++++++++++++--
>  arch/x86/kernel/cpu/sgx/sgx.h  |  2 +
>  4 files changed, 128 insertions(+), 8 deletions(-)
> 
> -- 
> 2.20.1
> 

I've tested also these. Looking at the feedback, there's
nothing game changing, so you could add for the next
version:

Tested-by: Jarkko Sakkinen <jarkko@kernel.org>

/Jarkko