[RFC] efi: Let architectures decide the flags that should be saved/restored

[Julien Thierry]

Currently, irqflags are saved before calling runtime services and
checked for mismatch on return.

Add a config option to let architectures define a set of flags to be
checked and (if needed) restored when coming back from runtime services.
This allows to use check flags that are not necesarly related to
irqflags.

Signed-off-by: Julien Thierry <julien.thierry@xxxxxxx>
---
 arch/Kconfig                            |  8 ++++++++
 drivers/firmware/efi/runtime-wrappers.c |  4 ++--
 include/linux/efi.h                     | 12 ++++++++++--
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index e1e540f..cbec325 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -695,6 +695,14 @@ config HAVE_ARCH_HASH
 	  file which provides platform-specific implementations of some
 	  functions in <linux/hash.h> or fs/namei.c.
 
+config HAVE_GENERIC_EFI_FLAGS
+	bool
+	default n
+	help
+	  Architecture defines a set of flags that EFI runtime services
+	  should take care to restore when returning to the OS.
+	  If this is not set, the set of flags defaults to the arch irqflags.
+
 config ISA_BUS_API
 	def_bool ISA
 
diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
index 8903b9c..6dafa04 100644
--- a/drivers/firmware/efi/runtime-wrappers.c
+++ b/drivers/firmware/efi/runtime-wrappers.c
@@ -93,7 +93,7 @@ void efi_call_virt_check_flags(unsigned long flags, const char *call)
 {
 	unsigned long cur_flags, mismatch;
 
-	local_save_flags(cur_flags);
+	efi_save_flags(cur_flags);
 
 	mismatch = flags ^ cur_flags;
 	if (!WARN_ON_ONCE(mismatch & ARCH_EFI_IRQ_FLAGS_MASK))
@@ -102,7 +102,7 @@ void efi_call_virt_check_flags(unsigned long flags, const char *call)
 	add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_NOW_UNRELIABLE);
 	pr_err_ratelimited(FW_BUG "IRQ flags corrupted (0x%08lx=>0x%08lx) by EFI %s\n",
 			   flags, cur_flags, call);
-	local_irq_restore(flags);
+	efi_restore_flags(flags);
 }
 
 /*
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 100ce4a..41c110a 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1594,6 +1594,14 @@ enum efi_secureboot_mode {
 
 void efi_retrieve_tpm2_eventlog(efi_system_table_t *sys_table);
 
+#ifdef CONFIG_HAVE_GENERIC_EFI_FLAGS
+#define efi_save_flags(state_flags)	arch_efi_save_flags(state_flags)
+#define efi_restore_flags(state_flags)	arch_efi_restore_flags(state_flags)
+#else
+#define efi_save_flags(state_flags)	local_save_flags(state_flags)
+#define efi_restore_flags(state_flags)	local_irq_restore(state_flags)
+#endif
+
 /*
  * Arch code can implement the following three template macros, avoiding
  * reptition for the void/non-void return cases of {__,}efi_call_virt():
@@ -1621,7 +1629,7 @@ enum efi_secureboot_mode {
 									\
 	arch_efi_call_virt_setup();					\
 									\
-	local_save_flags(__flags);					\
+	efi_save_flags(__flags);					\
 	__s = arch_efi_call_virt(p, f, args);				\
 	efi_call_virt_check_flags(__flags, __stringify(f));		\
 									\
@@ -1636,7 +1644,7 @@ enum efi_secureboot_mode {
 									\
 	arch_efi_call_virt_setup();					\
 									\
-	local_save_flags(__flags);					\
+	efi_save_flags(__flags);					\
 	arch_efi_call_virt(p, f, args);					\
 	efi_call_virt_check_flags(__flags, __stringify(f));		\
 									\
-- 
1.9.1




-- 
Julien Thierry