linux-kernel - Re: [PATCH v3 02/28] x86/sgx: Add EPC page flags to identify owner type

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Message-Id: <CU4GFR4WLMZP.3R9HJQFFG1JEK@seitikki>
Date:   Mon, 17 Jul 2023 12:43:31 +0000
From:   "Jarkko Sakkinen" <jarkko@...nel.org>
To:     "Jarkko Sakkinen" <jarkko@...nel.org>,
        "Haitao Huang" <haitao.huang@...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>
Cc:     <kai.huang@...el.com>, <reinette.chatre@...el.com>,
        "Sean Christopherson" <sean.j.christopherson@...el.com>,
        <zhiquan1.li@...el.com>, <kristen@...ux.intel.com>,
        <seanjc@...gle.com>
Subject: Re: [PATCH v3 02/28] x86/sgx: Add EPC page flags to identify owner
 type

On Mon Jul 17, 2023 at 12:41 PM UTC, Jarkko Sakkinen wrote:
> On Wed Jul 12, 2023 at 11:01 PM UTC, Haitao Huang wrote:
> > From: Sean Christopherson <sean.j.christopherson@...el.com>
> >
> > Two types of owners, 'sgx_encl' for VA pages and 'sgx_encl_page' for other,
> > can be stored in the union field in sgx_epc_page struct introduced in the
> > previous patch.
>
> This would be easier to follow:
>
> "Two types of owners of struct_epc_page, 'sgx_encl' for VA pages and
> 'sgx_encl_page' can be stored in the previously introduced union field."
>
> > When cgroup OOM support is added in a later patch, the owning enclave of a
> > page will need to be identified. Retrieving the sgx_encl struct from a
> > sgx_epc_page will be different if the page is a VA page vs. other enclave
> > pages.
> >
> > Add 2 flags which will identify the type of the owner and apply them
> > accordingly to newly allocated pages.
>
> This would be easier to follow:
>
> "OOM support for cgroups requires that the owner needs to be identified
> when selecting pages from the unreclaimable list. Address this by adding
> flags for identifying the owner type."
>
> It is better to carry the story a little bit forward than say that a
> subsequent patch will require this :-) I.e. enough to get at least a
> rough idea what is going on.

Oops, sent by mistake. I was going to say that the flag would be better
named simply as SGX_EPC_OWNER_PAGE instead of SGX_EPC_OWNER_ENCL_PAGE.

BR, Jarkko