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== Problem == The amount of SGX memory on a system is determined by the BIOS and it varies wildly between systems. It can be as small as dozens of MB's and as large as many GB's on servers. Just like how applications need to know how much regular RAM is available, enclave builders need to know how much SGX memory an enclave can consume. == Solution == Introduce a new sysfs file: /sys/devices/system/node/nodeX/x86/sgx_total_bytes to enumerate the amount of SGX memory available in each NUMA node. This serves the same function for SGX as /proc/meminfo or /sys/devices/system/node/nodeX/meminfo does for normal RAM. 'sgx_total_bytes' is needed today to help drive the SGX selftests. SGX-specific swap code is exercised by creating overcommitted enclaves which are larger than the physical SGX memory on the system. They currently use a CPUID-based approach which can diverge from the actual amount of SGX memory available. 'sgx_total_bytes' ensures that the selftests can work efficiently and do not attempt stupid things like creating a 100,000 MB enclave on a system with 128 MB of SGX memory. == Implementation Details == Introduce CONFIG_HAVE_ARCH_NODE_DEV_GROUP opt-in flag to expose an arch specific attribute group, and add an attribute for the amount of SGX memory in bytes to each NUMA node: == ABI Design Discussion == As opposed to the per-node ABI, a single, global ABI was considered. However, this would prevent enclaves from being able to size themselves so that they fit on a single NUMA node. Essentially, a single value would rule out NUMA optimizations for enclaves. Create a new "x86/" directory inside each "nodeX/" sysfs directory. 'sgx_total_bytes' is expected to be the first of at least a few sgx-specific files to be placed in the new directory. Just scanning /proc/meminfo, these are the no-brainers that we have for RAM, but we need for SGX: MemTotal: xxxx kB // sgx_total_bytes (implemented here) MemFree: yyyy kB // sgx_free_bytes SwapTotal: zzzz kB // sgx_swapped_bytes So, at *least* three. I think we will eventually end up needing something more along the lines of a dozen. A new directory (as opposed to being in the nodeX/ "root") directory avoids cluttering the root with several "sgx_*" files. Place the new file in a new "nodeX/x86/" directory because SGX is highly x86-specific. It is very unlikely that any other architecture (or even non-Intel x86 vendor) will ever implement SGX. Using "sgx/" as opposed to "x86/" was also considered. But, there is a real chance this can get used for other arch-specific purposes. [ dhansen: rewrite changelog ] Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211116162116.93081-2-jarkko@kernel.org
65 lines
1.3 KiB
C
65 lines
1.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_NUMA_H
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#define _LINUX_NUMA_H
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#include <linux/types.h>
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#ifdef CONFIG_NODES_SHIFT
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#define NODES_SHIFT CONFIG_NODES_SHIFT
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#else
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#define NODES_SHIFT 0
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#endif
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#define MAX_NUMNODES (1 << NODES_SHIFT)
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#define NUMA_NO_NODE (-1)
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/* optionally keep NUMA memory info available post init */
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#ifdef CONFIG_NUMA_KEEP_MEMINFO
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#define __initdata_or_meminfo
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#else
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#define __initdata_or_meminfo __initdata
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#endif
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#ifdef CONFIG_NUMA
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#include <linux/printk.h>
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#include <asm/sparsemem.h>
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/* Generic implementation available */
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int numa_map_to_online_node(int node);
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#ifndef memory_add_physaddr_to_nid
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static inline int memory_add_physaddr_to_nid(u64 start)
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{
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pr_info_once("Unknown online node for memory at 0x%llx, assuming node 0\n",
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start);
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return 0;
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}
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#endif
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#ifndef phys_to_target_node
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static inline int phys_to_target_node(u64 start)
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{
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pr_info_once("Unknown target node for memory at 0x%llx, assuming node 0\n",
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start);
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return 0;
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}
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#endif
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#else /* !CONFIG_NUMA */
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static inline int numa_map_to_online_node(int node)
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{
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return NUMA_NO_NODE;
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}
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static inline int memory_add_physaddr_to_nid(u64 start)
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{
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return 0;
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}
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static inline int phys_to_target_node(u64 start)
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{
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return 0;
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}
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#endif
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#ifdef CONFIG_HAVE_ARCH_NODE_DEV_GROUP
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extern const struct attribute_group arch_node_dev_group;
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#endif
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#endif /* _LINUX_NUMA_H */
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