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Date: Mon, 26 Dec 2022 20:43:58 +0000 From: Jarkko Sakkinen <jarkko@...nel.org> To: Sean Christopherson <seanjc@...gle.com> Cc: Dave Hansen <dave.hansen@...el.com>, Kristen Carlson Accardi <kristen@...ux.intel.com>, 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 Mon, Dec 12, 2022 at 06:09:39PM +0000, Sean Christopherson wrote: > 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. When swapping VA pages the topology of the VA page cache for swapped VA pages is the main question. It is compromise between how long swap-in and swap-out can take, and how generic solution it be, meaning how deep hierarchies you want to build, or is just a flat list of parent VA pages "good enough". Also, there's the question whether it should be a global cache, per cgroup and so forth. Implementing any solution is not overly complicated. Locking in these options is what puzzles me. BR, Jarkko
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