[PATCH V3 1/3] x86/efi: Call efi_delete_dummy_variable() after creating efi_rts_wq

[Sai Praneeth Prakhya]

From: Sai Praneeth <sai.praneeth.prakhya@xxxxxxxxx>

Create a workqueue named efi_rts_wq (efi runtime services workqueue), so
that all efi_runtime_services() are executed in kthread context.

Invoking efi_runtime_services() through efi_rts_wq means all accesses to
efi_runtime_services() should be done after efi_rts_wq has been created.
efi_delete_dummy_variable() calls set_variable(), hence
efi_delete_dummy_variable() should be called after efi_rts_wq has been
created.

Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@xxxxxxxxx>
Suggested-by: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Lee Chun-Yi <jlee@xxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
Cc: Naresh Bhat <naresh.bhat@xxxxxxxxxx>
Cc: Ricardo Neri <ricardo.neri@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ravi Shankar <ravi.v.shankar@xxxxxxxxx>
Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx>
---
 arch/x86/platform/efi/efi.c        | 15 +++++++++------
 drivers/firmware/efi/arm-runtime.c |  3 +++
 drivers/firmware/efi/efi.c         | 25 +++++++++++++++++++++++++
 include/linux/efi.h                |  4 ++++
 4 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 9061babfbc83..adcc55cd25ce 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -893,9 +893,6 @@ static void __init kexec_enter_virtual_mode(void)
 
 	if (efi_enabled(EFI_OLD_MEMMAP) && (__supported_pte_mask & _PAGE_NX))
 		runtime_code_page_mkexec();
-
-	/* clean DUMMY object */
-	efi_delete_dummy_variable();
 #endif
 }
 
@@ -1015,9 +1012,6 @@ static void __init __efi_enter_virtual_mode(void)
 	 * necessary relocation fixups for the new virtual addresses.
 	 */
 	efi_runtime_update_mappings();
-
-	/* clean DUMMY object */
-	efi_delete_dummy_variable();
 }
 
 void __init efi_enter_virtual_mode(void)
@@ -1031,6 +1025,15 @@ void __init efi_enter_virtual_mode(void)
 		__efi_enter_virtual_mode();
 
 	efi_dump_pagetable();
+
+	if (!efi_create_rts_wq())
+		return;
+
+	/*
+	 * Clean DUMMY object calls EFI Runtime Service, set_variable(), so
+	 * it should be invoked only after efi_rts_wq is ready.
+	 */
+	efi_delete_dummy_variable();
 }
 
 static int __init arch_parse_efi_cmdline(char *str)
diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
index 5889cbea60b8..6fb06130b53f 100644
--- a/drivers/firmware/efi/arm-runtime.c
+++ b/drivers/firmware/efi/arm-runtime.c
@@ -139,6 +139,9 @@ static int __init arm_enable_runtime_services(void)
 		return -ENOMEM;
 	}
 
+	if (!efi_create_rts_wq())
+		return 0;
+
 	/* Set up runtime services function pointers */
 	efi_native_runtime_setup();
 	set_bit(EFI_RUNTIME_SERVICES, &efi.flags);
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 232f4915223b..b9103caa03b4 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -84,6 +84,8 @@ struct mm_struct efi_mm = {
 	.mmlist			= LIST_HEAD_INIT(efi_mm.mmlist),
 };
 
+struct workqueue_struct *efi_rts_wq;
+
 static bool disable_runtime;
 static int __init setup_noefi(char *arg)
 {
@@ -337,6 +339,13 @@ static int __init efisubsys_init(void)
 	if (!efi_enabled(EFI_BOOT))
 		return 0;
 
+	/*
+	 * If we failed to create efi_rts_wq, EFI_RUNTIME_SERVICES would
+	 * have been be cleared, check for that condition.
+	 */
+	if (!efi_enabled(EFI_RUNTIME_SERVICES))
+		return 0;
+
 	/* We register the efi directory at /sys/firmware/efi */
 	efi_kobj = kobject_create_and_add("efi", firmware_kobj);
 	if (!efi_kobj) {
@@ -971,3 +980,19 @@ static int register_update_efi_random_seed(void)
 }
 late_initcall(register_update_efi_random_seed);
 #endif
+
+bool __init efi_create_rts_wq(void)
+{
+	/*
+	 * Since we process only one efi_runtime_service() at a time, an
+	 * ordered workqueue (which creates only one execution context)
+	 * should suffice all our needs.
+	 */
+	efi_rts_wq = alloc_ordered_workqueue("efi_rts_wq", 0);
+	if (!efi_rts_wq) {
+		pr_err("Creating efi_rts_wq failed, EFI runtime services disabled.\n");
+		clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
+		return false;
+	}
+	return true;
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 3016d8c456bc..565955010b18 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -987,6 +987,7 @@ extern void efi_map_pal_code (void);
 extern void efi_memmap_walk (efi_freemem_callback_t callback, void *arg);
 extern void efi_gettimeofday (struct timespec64 *ts);
 extern void efi_enter_virtual_mode (void);	/* switch EFI to virtual mode, if possible */
+extern bool __init efi_create_rts_wq(void);
 #ifdef CONFIG_X86
 extern void efi_late_init(void);
 extern void efi_free_boot_services(void);
@@ -1651,4 +1652,7 @@ struct linux_efi_tpm_eventlog {
 
 extern int efi_tpm_eventlog_init(void);
 
+/* Workqueue to queue EFI Runtime Services */
+extern struct workqueue_struct *efi_rts_wq;
+
 #endif /* _LINUX_EFI_H */
-- 
2.7.4