arm64/efi: Drop efi_rt_lock spinlock from EFI arch wrapper

Since commit

  5894cf5 ("acpi/prmt: Use EFI runtime sandbox to invoke PRM handlers")

all EFI runtime calls on arm64 are routed via the EFI runtime wrappers,
which are serialized using the efi_runtime_lock semaphore.

This means the efi_rt_lock spinlock in the arm64 arch wrapper code has
become redundant, and can be dropped. For robustness, replace it with an
assert that the EFI runtime lock is in fact held by 'current'.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: ardbiesheuvel

arch/arm64/kernel/efi.c

@@ -165,19 +165,16 @@ asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
 	return s;
 }
 
-static DEFINE_RAW_SPINLOCK(efi_rt_lock);
-
 void arch_efi_call_virt_setup(void)
 {
+	efi_runtime_assert_lock_held();
 	efi_virtmap_load();
-	raw_spin_lock(&efi_rt_lock);
 	__efi_fpsimd_begin();
 }
 
 void arch_efi_call_virt_teardown(void)
 {
 	__efi_fpsimd_end();
-	raw_spin_unlock(&efi_rt_lock);
 	efi_virtmap_unload();
 }