x86/sgx: Initialize metadata for Enclave Page Cache (EPC) sections

Although carved out of normal DRAM, enclave memory is marked in the
system memory map as reserved and is not managed by the core mm.  There
may be several regions spread across the system.  Each contiguous region
is called an Enclave Page Cache (EPC) section.  EPC sections are
enumerated via CPUID

Enclave pages can only be accessed when they are mapped as part of an
enclave, by a hardware thread running inside the enclave.

Parse CPUID data, create metadata for EPC pages and populate a simple
EPC page allocator.  Although much smaller, ‘struct sgx_epc_page’
metadata is the SGX analog of the core mm ‘struct page’.

Similar to how the core mm’s page->flags encode zone and NUMA
information, embed the EPC section index to the first eight bits of
sgx_epc_page->desc.  This allows a quick reverse lookup from EPC page to
EPC section.  Existing client hardware supports only a single section,
while upcoming server hardware will support at most eight sections.
Thus, eight bits should be enough for long term needs.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Co-developed-by: Serge Ayoun <serge.ayoun@intel.com>
Signed-off-by: Serge Ayoun <serge.ayoun@intel.com>
Co-developed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Jethro Beekman <jethro@fortanix.com>
Link: https://lkml.kernel.org/r/20201112220135.165028-6-jarkko@kernel.org

1 files changed, 60 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
new file mode 100644
index 000000000000..02afa84dd8fd
--- /dev/null
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _X86_SGX_H
+#define _X86_SGX_H
+
+#include <linux/bitops.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/rwsem.h>
+#include <linux/types.h>
+#include <asm/asm.h>
+#include "arch.h"
+
+#undef pr_fmt
+#define pr_fmt(fmt) "sgx: " fmt
+
+#define SGX_MAX_EPC_SECTIONS		8
+
+struct sgx_epc_page {
+	unsigned int section;
+	struct list_head list;
+};
+
+/*
+ * 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.
+ */
+struct sgx_epc_section {
+	unsigned long phys_addr;
+	void *virt_addr;
+	struct list_head page_list;
+	struct list_head laundry_list;
+	struct sgx_epc_page *pages;
+	spinlock_t lock;
+};
+
+extern struct sgx_epc_section sgx_epc_sections[SGX_MAX_EPC_SECTIONS];
+
+static inline unsigned long sgx_get_epc_phys_addr(struct sgx_epc_page *page)
+{
+	struct sgx_epc_section *section = &sgx_epc_sections[page->section];
+	unsigned long index;
+
+	index = ((unsigned long)page - (unsigned long)section->pages) / sizeof(*page);
+
+	return section->phys_addr + index * PAGE_SIZE;
+}
+
+static inline void *sgx_get_epc_virt_addr(struct sgx_epc_page *page)
+{
+	struct sgx_epc_section *section = &sgx_epc_sections[page->section];
+	unsigned long index;
+
+	index = ((unsigned long)page - (unsigned long)section->pages) / sizeof(*page);
+
+	return section->virt_addr + index * PAGE_SIZE;
+}
+
+#endif /* _X86_SGX_H */