linux-kernel - Re: [PATCH v9 2/2] x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node

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Message-ID: <YXwK7Wdi1VUK+1LS@kroah.com>
Date:   Fri, 29 Oct 2021 16:53:33 +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>, reinette.chatre@...el.com,
        tony.luck@...el.com, linux-kernel@...r.kernel.org,
        linux-sgx@...r.kernel.org
Subject: Re: [PATCH v9 2/2] x86/sgx: Add an attribute for the amount of SGX
 memory in a NUMA node

On Fri, Oct 29, 2021 at 03:18:57PM +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 an attribute for the amount of SGX memory in bytes to each NUMA
> node. The path is /sys/devices/system/node/node[0-9]*/sgx/size.
> Calculate these values by summing up EPC section sizes for each node
> during the driver initalization.
> 
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
> ---
> v9:
> * Fix racy initialization of sysfs attributes:
>   https://lore.kernel.org/linux-sgx/YXOsx8SvFJV5R7lU@kroah.com/
> 
> v8:
> * Fix a bug in sgx_numa_init(): node->dev should be only set after
>   sysfe_create_group().  Otherwise, sysfs_remove_group() will issue a
>   warning in sgx_numa_exit(), when sgx_create_group() is unsuccessful,
>   because the group does not exist.
> 
> v7:
> * Shorten memory_size to size. The prefix makes the name only longer
>   but does not clarify things more than "size" would.
> * Use device_attribute instead of kobj_attribute.
> * Use named attribute group instead of creating raw kobject just for
>   the "sgx" subdirectory.
> 
> v6:
> * Initialize node->size to zero in sgx_setup_epc_section(), when the
>   node is first accessed.
> 
> v5
> * A new patch based on the discussion on
>   https://lore.kernel.org/linux-sgx/3a7cab4115b4f902f3509ad8652e616b91703e1d.camel@kernel.org/T/#t
> ---
>  Documentation/ABI/stable/sysfs-devices-node |  7 +++++
>  arch/x86/include/asm/sgx.h                  |  2 ++
>  arch/x86/kernel/cpu/sgx/main.c              | 31 +++++++++++++++++++++
>  arch/x86/kernel/cpu/sgx/sgx.h               |  2 ++
>  drivers/base/node.c                         | 16 ++++++++++-
>  5 files changed, 57 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/ABI/stable/sysfs-devices-node b/Documentation/ABI/stable/sysfs-devices-node
> index 484fc04bcc25..12dc2149e8e0 100644
> --- a/Documentation/ABI/stable/sysfs-devices-node
> +++ b/Documentation/ABI/stable/sysfs-devices-node
> @@ -176,3 +176,10 @@ Contact:	Keith Busch <keith.busch@...el.com>
>  Description:
>  		The cache write policy: 0 for write-back, 1 for write-through,
>  		other or unknown.
> +
> +What:		/sys/devices/system/node/nodeX/sgx/size
> +Date:		October 2021
> +Contact:	Jarkko Sakkinen <jarkko@...nel.org>
> +Description:
> +		Total available physical SGX memory, also known as Enclave Page
> +		Cache (EPC), in bytes.
> diff --git a/arch/x86/include/asm/sgx.h b/arch/x86/include/asm/sgx.h
> index 05f3e21f01a7..43d1ccae6c62 100644
> --- a/arch/x86/include/asm/sgx.h
> +++ b/arch/x86/include/asm/sgx.h
> @@ -365,6 +365,8 @@ struct sgx_sigstruct {
>   * comment!
>   */
>  
> +extern const struct attribute_group sgx_node_group;
> +
>  #ifdef CONFIG_X86_SGX_KVM
>  int sgx_virt_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs,
>  		     int *trapnr);
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index a6e313f1a82d..86d6d309ff29 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -714,9 +714,12 @@ static bool __init sgx_page_cache_init(void)
>  			spin_lock_init(&sgx_numa_nodes[nid].lock);
>  			INIT_LIST_HEAD(&sgx_numa_nodes[nid].free_page_list);
>  			node_set(nid, sgx_numa_mask);
> +			sgx_numa_nodes[nid].size = 0;
>  		}
>  
>  		sgx_epc_sections[i].node =  &sgx_numa_nodes[nid];
> +		sgx_numa_nodes[nid].dev = &node_devices[nid]->dev;
> +		sgx_numa_nodes[nid].size += size;
>  
>  		sgx_nr_epc_sections++;
>  	}
> @@ -790,6 +793,34 @@ int sgx_set_attribute(unsigned long *allowed_attributes,
>  }
>  EXPORT_SYMBOL_GPL(sgx_set_attribute);
>  
> +#ifdef CONFIG_NUMA
> +static ssize_t size_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	unsigned long size = 0;
> +	int nid;
> +
> +	for (nid = 0; nid < num_possible_nodes(); nid++) {
> +		if (dev == sgx_numa_nodes[nid].dev) {
> +			size = sgx_numa_nodes[nid].size;
> +			break;
> +		}
> +	}
> +
> +	return sysfs_emit(buf, "%lu\n", size);
> +}
> +DEVICE_ATTR_RO(size);

static?