x86/sgx: Log information when a node lacks an EPC section

JIRA: https://issues.redhat.com/browse/RHEL-22826
Upstream Status: merged into the linux.git

commit c8ddc99
Author: Aaron Lu <aaron.lu@intel.com>
Date:   Thu Sep 5 16:08:55 2024 +0800

    x86/sgx: Log information when a node lacks an EPC section

    For optimized performance, firmware typically distributes EPC sections
    evenly across different NUMA nodes. However, there are scenarios where
    a node may have both CPUs and memory but no EPC section configured. For
    example, in an 8-socket system with a Sub-Numa-Cluster=2 setup, there
    are a total of 16 nodes. Given that the maximum number of supported EPC
    sections is 8, it is simply not feasible to assign one EPC section to
    each node. This configuration is not incorrect - SGX will still operate
    correctly; it is just not optimized from a NUMA standpoint.

    For this reason, log a message when a node with both CPUs and memory
    lacks an EPC section. This will provide users with a hint as to why they
    might be experiencing less-than-ideal performance when running SGX
    enclaves.

    Suggested-by: Dave Hansen <dave.hansen@intel.com>
    Signed-off-by: Aaron Lu <aaron.lu@intel.com>
    Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
    Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
    Acked-by: Kai Huang <kai.huang@intel.com>
    Link: https://lore.kernel.org/all/20240905080855.1699814-3-aaron.lu%40intel.com

Signed-off-by: Vladis Dronov <vdronov@redhat.com>

Author: nefigtut

arch/x86/kernel/cpu/sgx/main.c

@@ -847,6 +847,13 @@ static bool __init sgx_page_cache_init(void)
 		return false;
 	}
 
+	for_each_online_node(nid) {
+		if (!node_isset(nid, sgx_numa_mask) &&
+		    node_state(nid, N_MEMORY) && node_state(nid, N_CPU))
+			pr_info("node%d has both CPUs and memory but doesn't have an EPC section\n",
+				nid);
+	}
+
 	return true;
 }