linux-kernel - Re: [PATCH v2 14/18] x86/sgx: Add EPC OOM path to forcefully reclaim EPC

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Date:   Mon, 12 Dec 2022 18:09:39 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Kristen Carlson Accardi <kristen@...ux.intel.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        dave.hansen@...ux.intel.com, tj@...nel.org,
        linux-kernel@...r.kernel.org, linux-sgx@...r.kernel.org,
        cgroups@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        zhiquan1.li@...el.com
Subject: Re: [PATCH v2 14/18] x86/sgx: Add EPC OOM path to forcefully reclaim
 EPC

On Fri, Dec 09, 2022, Dave Hansen wrote:
> On 12/9/22 08:05, Kristen Carlson Accardi wrote:
> > Aside from that though, I don't think that killing enclaves makes sense
> > outside the context of cgroup limits. 
> 
> I think it makes a lot of sense in theory.  Whatever situation we get
> into with a cgroup's EPC we can also get into with the whole system's EPC.
> 
> *But*, it's orders of magnitude harder to hit on the whole system.

...

> If someone wants to extend this OOM support to system-wide EPC later, then go
> ahead.  But, I don't think it makes a lot of sense to invert this series for
> it.

+1 from the peanut gallery.  With VMM EPC oversubscription suport, no sane VMM
will oversubscribe VEPC pages.  And for VA pages, supporting swap of VA pages is
likely a more userspace-friendly approach if system-wide EPC OOM is a concern.