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Date:   Thu, 17 Sep 2020 19:09:40 -0700
From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     Haitao Huang <haitao.huang@linux.intel.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>, x86@kernel.org,
        linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org,
        Jethro Beekman <jethro@fortanix.com>,
        Chunyang Hui <sanqian.hcy@antfin.com>,
        Jordan Hand <jorhand@linux.microsoft.com>,
        Nathaniel McCallum <npmccallum@redhat.com>,
        Seth Moore <sethmo@google.com>,
        Darren Kenny <darren.kenny@oracle.com>,
        Suresh Siddha <suresh.b.siddha@intel.com>,
        akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com,
        asapek@google.com, bp@alien8.de, cedric.xing@intel.com,
        chenalexchen@google.com, conradparker@google.com,
        cyhanish@google.com, dave.hansen@intel.com, haitao.huang@intel.com,
        josh@joshtriplett.org, kai.huang@intel.com, kai.svahn@intel.com,
        kmoy@google.com, ludloff@google.com, luto@kernel.org,
        nhorman@redhat.com, puiterwijk@redhat.com, rientjes@google.com,
        tglx@linutronix.de, yaozhangx@google.com
Subject: Re: [PATCH v38 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES
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On Thu, Sep 17, 2020 at 01:35:10PM -0500, Haitao Huang wrote:
> On Thu, 17 Sep 2020 11:02:06 -0500, Jarkko Sakkinen
> <jarkko.sakkinen@linux.intel.com> wrote:
> > 
> > Right, I do get the OOM case but wouldn't in that case the reasonable
> > thing to do destroy the enclave that is not even running? I mean that
> > means that we are globally out of EPC.
> > 
> 
> I would say it could be a policy, but not the only one. If it does not make
> much difference to kernel, IMHO we should  not set it in stone now.
> Debugging is also huge benefit to me.

Agreed, an EPC cgroup is the proper way to define/enforce what happens when
there is EPC pressure.  E.g. if process A is consuming 99% of the EPC, then
it doesn't make sense to unconditionally kill enclaves from process B.  If
the admin wants to give process A priority, so be it, but such a decision
shouldn't be baked into the kernel.

This series obviously doesn't provide an EPC cgroup, but that doesn't mean
we can't make decisions that will play nice with a cgroup in the future.