linux-kernel - Re: [PATCH v4 1/3] x86/sgx: Report SGX memory in /sys/devices/system/node/node*/meminfo

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Date:   Fri, 10 Sep 2021 08:51:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     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>,
        "Rafael J. Wysocki" <rafael@...nel.org>, linux-sgx@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/3] x86/sgx: Report SGX memory in
 /sys/devices/system/node/node*/meminfo

On Fri, Sep 10, 2021 at 03:17:24AM +0300, 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 /sys/devices/system/node/node*/meminfo,
> showing the total SGX memory in each NUMA node. The total memory for
> each NUMA node is calculated by adding the sizes of contained EPC
> sections together.
> 
> Introduce arch_node_read_meminfo(), which can optionally be rewritten by
> the arch code, and rewrite it for x86 so it prints SGX_MemTotal.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
> ---
> v4:
> * A new patch.
>  arch/x86/kernel/cpu/sgx/main.c | 14 ++++++++++++++
>  arch/x86/kernel/cpu/sgx/sgx.h  |  6 ++++++
>  drivers/base/node.c            | 10 +++++++++-
>  3 files changed, 29 insertions(+), 1 deletion(-)

Where is the Documentation/ABI/ update for this new sysfs file?

> 
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index 63d3de02bbcc..4c6da5f4a9d4 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -717,6 +717,7 @@ static bool __init sgx_page_cache_init(void)
>  		}
>  
>  		sgx_epc_sections[i].node =  &sgx_numa_nodes[nid];
> +		sgx_numa_nodes[nid].size += size;
>  
>  		sgx_nr_epc_sections++;
>  	}
> @@ -790,6 +791,19 @@ int sgx_set_attribute(unsigned long *allowed_attributes,
>  }
>  EXPORT_SYMBOL_GPL(sgx_set_attribute);
>  
> +ssize_t arch_node_read_meminfo(struct device *dev,
> +			       struct device_attribute *attr,
> +			       char *buf, int len)
> +{
> +	struct sgx_numa_node *node = &sgx_numa_nodes[dev->id];
> +
> +	len += sysfs_emit_at(buf, len,
> +			     "Node %d SGX_MemTotal:   %8lu kB\n",
> +			     dev->id, node->size);

Wait, that is not how sysfs files work.  they are "one value per file"
Please do not have multiple values in a single sysfs file, that is not
acceptable at all.

thanks,

greg k-h