x86/sgx: Add a basic NUMA allocation scheme to sgx_alloc_epc_page()

Background
==========

SGX enclave memory is enumerated by the processor in contiguous physical
ranges called Enclave Page Cache (EPC) sections.  Currently, there is a
free list per section, but allocations simply target the lowest-numbered
sections.  This is functional, but has no NUMA awareness.

Fortunately, EPC sections are covered by entries in the ACPI SRAT table.
These entries allow each EPC section to be associated with a NUMA node,
just like normal RAM.

Solution
========

Implement a NUMA-aware enclave page allocator.  Mirror the buddy allocator
and maintain a list of enclave pages for each NUMA node.  Attempt to
allocate enclave memory first from local nodes, then fall back to other
nodes.

Note that the fallback is not as sophisticated as the buddy allocator
and is itself not aware of NUMA distances.  When a node's free list is
empty, it searches for the next-highest node with enclave pages (and
will wrap if necessary).  This could be improved in the future.

Other
=====

NUMA_KEEP_MEMINFO dependency is required for phys_to_target_node().

 [ Kai Huang: Do not return NULL from __sgx_alloc_epc_page() because
   callers do not expect that and that leads to a NULL ptr deref. ]

 [ dhansen: Fix an uninitialized 'nid' variable in
   __sgx_alloc_epc_page() as

   Reported-by: kernel test robot <lkp@intel.com>

   to avoid any potential allocations from the wrong NUMA node or even
   premature allocation failures. ]

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/lkml/158188326978.894464.217282995221175417.stgit@dwillia2-desk3.amr.corp.intel.com/
Link: https://lkml.kernel.org/r/20210319040602.178558-1-kai.huang@intel.com
Link: https://lkml.kernel.org/r/20210318214933.29341-1-dave.hansen@intel.com
Link: https://lkml.kernel.org/r/20210317235332.362001-2-jarkko.sakkinen@intel.com

1 files changed, 10 insertions, 6 deletions

diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
index bc8af0428640..653af8ca1a25 100644
--- a/arch/x86/kernel/cpu/sgx/sgx.h
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -30,21 +30,25 @@ struct sgx_epc_page {
 };
 
 /*
+ * Contains the tracking data for NUMA nodes having EPC pages. Most importantly,
+ * the free page list local to the node is stored here.
+ */
+struct sgx_numa_node {
+	struct list_head free_page_list;
+	spinlock_t lock;
+};
+
+/*
  * The firmware can define multiple chunks of EPC to the different areas of the
  * physical memory e.g. for memory areas of the each node. This structure is
  * used to store EPC pages for one EPC section and virtual memory area where
  * the pages have been mapped.
- *
- * 'lock' must be held before accessing 'page_list' or 'free_cnt'.
  */
 struct sgx_epc_section {
 	unsigned long phys_addr;
 	void *virt_addr;
 	struct sgx_epc_page *pages;
-
-	spinlock_t lock;
-	struct list_head page_list;
-	unsigned long free_cnt;
+	struct sgx_numa_node *node;
 };
 
 extern struct sgx_epc_section sgx_epc_sections[SGX_MAX_EPC_SECTIONS];