Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.31 as permitted sender) client-ip=23.128.96.31;
Content-Type: text/plain; charset=iso-8859-15; format=flowed; delsp=yes
To:     "Christopherson,, Sean" <seanjc@google.com>,
        "Huang, Kai" <kai.huang@intel.com>
Cc:     "Zhang, Bo" <zhanb@microsoft.com>,
        "linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
        "cgroups@vger.kernel.org" <cgroups@vger.kernel.org>,
        "yangjie@microsoft.com" <yangjie@microsoft.com>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "Li, Zhiquan1" <zhiquan1.li@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "tj@kernel.org" <tj@kernel.org>,
        "anakrish@microsoft.com" <anakrish@microsoft.com>,
        "jarkko@kernel.org" <jarkko@kernel.org>,
        "hpa@zytor.com" <hpa@zytor.com>,
        "mikko.ylinen@linux.intel.com" <mikko.ylinen@linux.intel.com>,
        "Mehta, Sohil" <sohil.mehta@intel.com>,
        "bp@alien8.de" <bp@alien8.de>, "x86@kernel.org" <x86@kernel.org>,
        "kristen@linux.intel.com" <kristen@linux.intel.com>
Subject: Re: [PATCH v5 12/18] x86/sgx: Add EPC OOM path to forcefully reclaim
 EPC
References: <20230923030657.16148-1-haitao.huang@linux.intel.com>
 <20230923030657.16148-13-haitao.huang@linux.intel.com>
 <1b265d0c9dfe17de2782962ed26a99cc9d330138.camel@intel.com>
 <ZSSZaFrxvCvR1SOy@google.com>
 <06142144151da06772a9f0cc195a3c8ffcbc07b7.camel@intel.com>
 <1f7a740f3acff8a04ec95be39864fb3e32d2d96c.camel@intel.com>
 <op.2clydbf8wjvjmi@hhuan26-mobl.amr.corp.intel.com>
 <631f34613bcc8b5aa41cf519fa9d76bcd57a7650.camel@intel.com>
 <op.2cpecbevwjvjmi@hhuan26-mobl.amr.corp.intel.com>
 <aa404549c7e292dd2ec93a5e6a8c9d6d880c06b3.camel@intel.com>
 <op.2cxatlafwjvjmi@hhuan26-mobl.amr.corp.intel.com>
 <35a7fde056037a40b3b4b170e2ecd45bf8c4ba9f.camel@intel.com>
Date:   Mon, 16 Oct 2023 19:10:09 -0500
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
From:   "Haitao Huang" <haitao.huang@linux.intel.com>
Organization: Intel
Message-ID: <op.2cxmq7c2wjvjmi@hhuan26-mobl.amr.corp.intel.com>
In-Reply-To: <35a7fde056037a40b3b4b170e2ecd45bf8c4ba9f.camel@intel.com>
User-Agent: Opera Mail/1.0 (Win32)
Precedence: bulk

On Mon, 16 Oct 2023 16:09:52 -0500, Huang, Kai <kai.huang@intel.com> wrote:
[...]

> still need to fix the bug mentioned above here.
>
> I really think you should just go this simple way:
>
> When you want to take EPC back from VM, kill the VM.
>

My only concern is that this is a compromise due to current limitation (no  
other sane way to take EPC from VMs). If we define this behavior and it  
becomes a contract to user space, then we can't change in future.

On the other hand, my understanding the reason you want this behavior is  
to enforce EPC limit at runtime. I just not sure how important it is and  
if it is a real usage given all limitations of SGX VMs we have (static EPC  
size, no migration).

Thanks

Haitao