Re: [PATCH v3 2/2] x86/sgx: Add SGX_MemTotal to /proc/meminfo

[Randy Dunlap]

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@xxxxxxxxxx>
>
> ---
> 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