[PATCH 4/5] efi/arm: defer persistent reservations until after paging_init()

[Ard Biesheuvel]

The new memory EFI reservation feature we introduced to allow memory
reservations to persist across kexec may trigger an unbounded number
of calls to memblock_reserve(). The memblock subsystem can deal with
this fine, but not before memblock resizing is enabled, which we can
only do after paging_init(), when the memory we reallocate the array
into is actually mapped.

So break out the memreserve table processing into a separate routine
and call it after paging_init() on arm64. On ARM, because of limited
reviewing bandwidth of the maintainer, we cannot currently fix this,
so instead, disable the EFI persistent memreserve entirely on ARM so
we can fix it later.

Tested-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
 arch/arm64/kernel/setup.c               | 1 +
 drivers/firmware/efi/efi.c              | 4 ++++
 drivers/firmware/efi/libstub/arm-stub.c | 3 +++
 include/linux/efi.h                     | 7 +++++++
 4 files changed, 15 insertions(+)

diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 953e316521fc..f4fc1e0544b7 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -313,6 +313,7 @@ void __init setup_arch(char **cmdline_p)
 	arm64_memblock_init();
 
 	paging_init();
+	efi_apply_persistent_mem_reservations();
 
 	acpi_table_upgrade();
 
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 249eb70691b0..72a4da76d274 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -592,7 +592,11 @@ int __init efi_config_parse_tables(void *config_tables, int count, int sz,
 
 		early_memunmap(tbl, sizeof(*tbl));
 	}
+	return 0;
+}
 
+int __init efi_apply_persistent_mem_reservations(void)
+{
 	if (efi.mem_reserve != EFI_INVALID_TABLE_ADDR) {
 		unsigned long prsv = efi.mem_reserve;
 
diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
index 30ac0c975f8a..3d36142cf812 100644
--- a/drivers/firmware/efi/libstub/arm-stub.c
+++ b/drivers/firmware/efi/libstub/arm-stub.c
@@ -75,6 +75,9 @@ void install_memreserve_table(efi_system_table_t *sys_table_arg)
 	efi_guid_t memreserve_table_guid = LINUX_EFI_MEMRESERVE_TABLE_GUID;
 	efi_status_t status;
 
+	if (IS_ENABLED(CONFIG_ARM))
+		return;
+
 	status = efi_call_early(allocate_pool, EFI_LOADER_DATA, sizeof(*rsv),
 				(void **)&rsv);
 	if (status != EFI_SUCCESS) {
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 845174e113ce..100ce4a4aff6 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1167,6 +1167,8 @@ static inline bool efi_enabled(int feature)
 extern void efi_reboot(enum reboot_mode reboot_mode, const char *__unused);
 
 extern bool efi_is_table_address(unsigned long phys_addr);
+
+extern int efi_apply_persistent_mem_reservations(void);
 #else
 static inline bool efi_enabled(int feature)
 {
@@ -1185,6 +1187,11 @@ static inline bool efi_is_table_address(unsigned long phys_addr)
 {
 	return false;
 }
+
+static inline int efi_apply_persistent_mem_reservations(void)
+{
+	return 0;
+}
 #endif
 
 extern int efi_status_to_err(efi_status_t status);
-- 
2.17.1