linux-kernel - Re: [PATCH v5 06/18] x86/sgx: Introduce EPC page states

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Message-ID: <0c296ec0011afc51b90d77db7a2b1ae0a239aff6.camel@intel.com>
Date:   Tue, 3 Oct 2023 20:03:48 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "mingo@...hat.com" <mingo@...hat.com>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
        "hpa@...or.com" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jarkko@...nel.org" <jarkko@...nel.org>,
        "bp@...en8.de" <bp@...en8.de>,
        "haitao.huang@...ux.intel.com" <haitao.huang@...ux.intel.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "tj@...nel.org" <tj@...nel.org>,
        "Mehta, Sohil" <sohil.mehta@...el.com>
CC:     "kristen@...ux.intel.com" <kristen@...ux.intel.com>,
        "anakrish@...rosoft.com" <anakrish@...rosoft.com>,
        "Li, Zhiquan1" <zhiquan1.li@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "mikko.ylinen@...ux.intel.com" <mikko.ylinen@...ux.intel.com>,
        "yangjie@...rosoft.com" <yangjie@...rosoft.com>,
        "Zhang, Bo" <zhanb@...rosoft.com>
Subject: Re: [PATCH v5 06/18] x86/sgx: Introduce EPC page states

On Mon, 2023-10-02 at 23:49 -0500, Haitao Huang wrote:
> On Wed, 27 Sep 2023 05:28:36 -0500, Huang, Kai <kai.huang@...el.com> wrote:
> 
> > On Fri, 2023-09-22 at 20:06 -0700, Haitao Huang wrote:
> > > Use the lower 3 bits in the flags field of sgx_epc_page struct to
> > > track EPC states in its life cycle and define an enum for possible
> > > states. More state(s) will be added later.
> > 
> > This patch does more than what the changelog claims to do.  AFAICT it  
> > does
> > below:
> > 
> >  1) Use the lower 3 bits to track EPC page status
> >  2) Rename SGX_EPC_PAGE_RECLAIMER_TRACKED to SGX_EPC_PAGE_RERCLAIMABLE
> >  3) Introduce a new state SGX_EPC_PAGE_UNRECLAIMABLE
> >  4) Track SECS and VA pages as SGX_EPC_PAGE_UNRECLAIMABLE
> > 
> > The changelog only says 1) IIUC.
> > 
> I don't quite get why you would view 3) as a separate item from 1).

1) is about using some method to track EPC page status, 3) is adding a new
state.

Why cannot they be separated?

> In my view, 4) is not done as long as there is not separate list to track  
> it.

You are literally doing below:

@@ -113,6 +113,9 @@ static int sgx_encl_create(struct sgx_encl *encl, struct
sgx_secs *secs)
 	encl->attributes = secs->attributes;
 	encl->attributes_mask = SGX_ATTR_UNPRIV_MASK;
 
+	sgx_record_epc_page(encl->secs.epc_page,
+			    SGX_EPC_PAGE_UNRECLAIMABLE);
+

Which obviously is tracking SECS as unreclaimable page here.

The only thing you are not doing now is to put to the actual list, which you
introduced in a later patch.

But why not just doing them together?