linux-kernel - Re: [PATCH v38 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD

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Message-ID: <20200918020940.GA14678@sjchrist-ice>
Date:   Thu, 17 Sep 2020 19:09:40 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Haitao Huang <haitao.huang@...ux.intel.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>, x86@...nel.org,
        linux-sgx@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jethro Beekman <jethro@...tanix.com>,
        Chunyang Hui <sanqian.hcy@...fin.com>,
        Jordan Hand <jorhand@...ux.microsoft.com>,
        Nathaniel McCallum <npmccallum@...hat.com>,
        Seth Moore <sethmo@...gle.com>,
        Darren Kenny <darren.kenny@...cle.com>,
        Suresh Siddha <suresh.b.siddha@...el.com>,
        akpm@...ux-foundation.org, andriy.shevchenko@...ux.intel.com,
        asapek@...gle.com, bp@...en8.de, cedric.xing@...el.com,
        chenalexchen@...gle.com, conradparker@...gle.com,
        cyhanish@...gle.com, dave.hansen@...el.com, haitao.huang@...el.com,
        josh@...htriplett.org, kai.huang@...el.com, kai.svahn@...el.com,
        kmoy@...gle.com, ludloff@...gle.com, luto@...nel.org,
        nhorman@...hat.com, puiterwijk@...hat.com, rientjes@...gle.com,
        tglx@...utronix.de, yaozhangx@...gle.com
Subject: Re: [PATCH v38 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES

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@...ux.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.