linux-kernel - Re: [PATCH v5 12/18] x86/sgx: Add EPC OOM path to forcefully reclaim EPC

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Message-ID: <op.2cztv1bewjvjmi@hhuan26-mobl.amr.corp.intel.com>
Date:   Tue, 17 Oct 2023 23:39:27 -0500
From:   "Haitao Huang" <haitao.huang@...ux.intel.com>
To:     Michal Koutný <mkoutny@...e.com>
Cc:     "Christopherson,, Sean" <seanjc@...gle.com>,
        "Huang, Kai" <kai.huang@...el.com>,
        "Zhang, Bo" <zhanb@...rosoft.com>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
        "yangjie@...rosoft.com" <yangjie@...rosoft.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "Li, Zhiquan1" <zhiquan1.li@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "tj@...nel.org" <tj@...nel.org>,
        "anakrish@...rosoft.com" <anakrish@...rosoft.com>,
        "jarkko@...nel.org" <jarkko@...nel.org>,
        "hpa@...or.com" <hpa@...or.com>,
        "mikko.ylinen@...ux.intel.com" <mikko.ylinen@...ux.intel.com>,
        "Mehta, Sohil" <sohil.mehta@...el.com>,
        "bp@...en8.de" <bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>,
        "kristen@...ux.intel.com" <kristen@...ux.intel.com>
Subject: Re: [PATCH v5 12/18] x86/sgx: Add EPC OOM path to forcefully reclaim
 EPC

On Tue, 17 Oct 2023 14:13:22 -0500, Michal Koutný <mkoutny@...e.com> wrote:

> On Tue, Oct 17, 2023 at 08:54:48PM +0200, Michal Koutný  
> <mkoutny@...e.com> wrote:
>> Is this distinction between preemptability of EPC pages mandated by the
>> HW implementation? (host/"process" enclaves vs VM enclaves) Or do have
>> users an option to lock certain pages in memory that yields this
>> difference?
>
> (After skimming Documentation/arch/x86/sgx.rst, Section "Virtual EPC")
>
> Or would these two types warrant also two types of miscresource? (To
> deal with each in own way.)

They are from the same bucket of HW resource so I think it's more suitable  
to be one resource type. Otherwise need to policy to dividing the  
capacity, etc. And it is still possible in future vEPC become reclaimable.

My current thinking is we probably can get away with non-preemptive  
max_write for enclaves too. See my other reply.

Thanks
Haitao