Re: [PATCH 0/4] x86/sgx: fine grained SGX MCA behavior

[Jarkko Sakkinen <jarkko@kernel.org>]

On Tue, May 10, 2022 at 11:16:46AM +0800, Zhiquan Li wrote:
> Hi everyone,
> 
> This series contains a few patches to fine grained SGX MCA behavior.
> 
> When VM guest access a SGX EPC page with memory failure, current
> behavior will kill the guest, expected only kill the SGX application
> inside it.
> 
> To fix it we send SIGBUS with code BUS_MCEERR_AR and some extra
> information for hypervisor to inject #MC information to guest, which
> is helpful in SGX virtualization case.
> 
> However, current SGX data structures are insufficient to track the
> EPC pages for vepc, so we introduce a new struct sgx_vepc_page which
> can be the owner of EPC pages for vepc and saves the useful info of
> EPC pages for vepc, like struct sgx_encl_page.
> 
> Moreover, canonical memory failure collects victim tasks by iterating
> all the tasks one by one and use reverse mapping to get victim tasks’
> virtual address. This is not necessary for SGX - as one EPC page can
> be mapped to ONE enclave only. So, this 1:1 mapping enforcement
> allows us to find task virtual address with physical address
> directly.

Hmm... An enclave can be shared by multiple processes. The virtual
address is the same but there can be variable number of processes
having it mapped.

> 
> Then we extend the solution for the normal SGX case, so that the task
> has opportunity to make further decision while EPC page has memory
> failure.
> 
> Tests:
> 1. MCE injection test for SGX in VM.
>    As we expected, the application was killed and VM was alive.
> 2. MCE injection test for SGX on host.
>    As we expected, the application received SIGBUS with extra info.
> 3. Kernel selftest/sgx: PASS
> 4. Internal SGX stress test: PASS
> 5. kmemleak test: No memory leakage detected.
> 
> Zhiquan Li (4):
>   x86/sgx: Move struct sgx_vepc definition to sgx.h
>   x86/sgx: add struct sgx_vepc_page to manage EPC pages for vepc
>   x86/sgx: Fine grained SGX MCA behavior for virtualization
>   x86/sgx: Fine grained SGX MCA behavior for normal case
> 
>  arch/x86/kernel/cpu/sgx/main.c | 24 ++++++++++++++++++++++--
>  arch/x86/kernel/cpu/sgx/sgx.h  | 12 ++++++++++++
>  arch/x86/kernel/cpu/sgx/virt.c | 29 +++++++++++++++++++----------
>  3 files changed, 53 insertions(+), 12 deletions(-)
> 
> -- 
> 2.25.1
> 

BR, Jarkko