[PATCH v2 2/6] x86/sgx: Add infrastructure to identify SGX EPC pages

[Tony Luck]

X86 machine check architecture reports a physical address when there
is a memory error. Handling that error requires a method to determine
whether the physical address reported is in any of the areas reserved
for EPC pages by BIOS.

Add an end_phys_addr field to the sgx_epc_section structure and a
new function sgx_paddr_to_page() that searches all such structures
and returns the struct sgx_epc_page pointer if the address is an EPC
page. This function is only intended for use within SGX code.

Export a function sgx_is_epc_page() that simply reports whether an
address is an EPC page for use elsewhere in the kernel.

Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
---
 arch/x86/kernel/cpu/sgx/main.c | 24 ++++++++++++++++++++++++
 arch/x86/kernel/cpu/sgx/sgx.h  |  1 +
 2 files changed, 25 insertions(+)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index d61bc1f635a1..41753f81a071 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -654,6 +654,7 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
 	}
 
 	section->phys_addr = phys_addr;
+	section->end_phys_addr = phys_addr + size - 1;
 
 	for (i = 0; i < nr_pages; i++) {
 		section->pages[i].section = index;
@@ -665,6 +666,29 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
 	return true;
 }
 
+static struct sgx_epc_page *sgx_paddr_to_page(u64 paddr)
+{
+	struct sgx_epc_section *section;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(sgx_epc_sections); i++) {
+		section = &sgx_epc_sections[i];
+
+		if (paddr < section->phys_addr || paddr > section->end_phys_addr)
+			continue;
+
+		return &section->pages[PFN_DOWN(paddr - section->phys_addr)];
+	}
+
+	return NULL;
+}
+
+bool sgx_is_epc_page(u64 paddr)
+{
+	return !!sgx_paddr_to_page(paddr);
+}
+EXPORT_SYMBOL_GPL(sgx_is_epc_page);
+
 /**
  * A section metric is concatenated in a way that @low bits 12-31 define the
  * bits 12-31 of the metric and @high bits 0-19 define the bits 32-51 of the
diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
index 4e1a410b8a62..226b081a4d05 100644
--- a/arch/x86/kernel/cpu/sgx/sgx.h
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -50,6 +50,7 @@ struct sgx_numa_node {
  */
 struct sgx_epc_section {
 	unsigned long phys_addr;
+	unsigned long end_phys_addr;
 	void *virt_addr;
 	struct sgx_epc_page *pages;
 	struct sgx_numa_node *node;
-- 
2.29.2