linux-kernel - Re: [PATCH v3 2/2] x86/sgx: Add SGX

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Message-ID: <ba483b7e-19a3-d4d3-56c0-3371a77341cb@infradead.org>
Date:   Wed, 25 Aug 2021 17:39:32 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Jarkko Sakkinen <jarkko@...nel.org>, linux-sgx@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Jonathan Corbet <corbet@....net>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 2/2] x86/sgx: Add SGX_MemTotal to /proc/meminfo

On 8/25/21 4:52 PM, Jarkko Sakkinen wrote:
> The amount of SGX memory on the system is determined by the BIOS and it
> varies wildly between systems.  It can be from dozens of MB's on desktops
> or VM's, up to many GB's on servers.  Just like for regular memory, it is
> sometimes useful to know the amount of usable SGX memory in the system.
> 
> Add SGX_MemTotal field to /proc/meminfo, which shows the total amount of
> usable SGX memory in the system.  E.g. with 32 MB reserved for SGX from
> BIOS, the printout would be:
> 
> SGX_MemTotal:      22528 kB
> 
> It is less than 32 MB because some of the space is reserved for Enclave
> Page Cache Metadata (EPCM), which contains state variables for all the
> pages in the Enclave Page Cache (EPC).  The latter contains the pages,
> which applications can use to create enclaves.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
> 
> ---
> v2:
> * Move ifdef fix for sgx_set_attribute() to a separate patch.
> ---
>   Documentation/x86/sgx.rst      | 6 ++++++
>   arch/x86/include/asm/sgx.h     | 2 ++
>   arch/x86/kernel/cpu/sgx/main.c | 7 ++++++-
>   arch/x86/mm/pat/set_memory.c   | 5 +++++
>   4 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/x86/sgx.rst b/Documentation/x86/sgx.rst
> index dd0ac96ff9ef..68ee171e1d8f 100644
> --- a/Documentation/x86/sgx.rst
> +++ b/Documentation/x86/sgx.rst
> @@ -250,3 +250,9 @@ user wants to deploy SGX applications both on the host and in guests
>   on the same machine, the user should reserve enough EPC (by taking out
>   total virtual EPC size of all SGX VMs from the physical EPC size) for
>   host SGX applications so they can run with acceptable performance.
> +
> +Supplemental fields for /proc/meminfo
> +=====================================
> +
> +SGX_MemTotal
> +	The total usable SGX protected memory in kilobytes.

Hi,

I would prefer to see this listed in Documentation/filesystems/proc.rst
as an optional field, depending on CONFIG_X86_SGX.
Or at least put a reference in proc.rst to this doc file and its
supplemental fields.

thanks.

-- 
~Randy