efi/arm64: FP/SIMD preserve/restore during UEFI Runtime Services

Two patches to add FP/SIMD preserve/restore to UEFI Runtime Services:
- patch #1 moves runtime services wrappers to generic code so we can reuse them for arm64
- patch #2 enables the wrappers for arm64 and inserts calls to kernel_neon_begin and kernel_neon_end

@Matt: please queue up for 3.17

v3:
- improve commit message for patch #2 and add Catalin's ack

v2:
- add Kconfig symbol EFI_RUNTIME_WRAPPERS so we don't break ia64 by enabling it unconditionally

Ard Biesheuvel (2):
efi/x86: move UEFI Runtime Services wrappers to generic code efi/arm64: preserve FP/SIMD registers on UEFI runtime services calls

 arch/arm64/Kconfig                      |   1 +
 arch/arm64/include/asm/efi.h            |  21 +++++
 arch/arm64/kernel/efi.c                 |  14 +--
 arch/x86/Kconfig                        |   1 +
 arch/x86/platform/efi/efi.c             | 144 +---------------------------
 drivers/firmware/efi/Kconfig            |   7 ++
 drivers/firmware/efi/Makefile           |   1 +
 drivers/firmware/efi/runtime-wrappers.c | 161 ++++++++++++++++++++++++++++++++
 include/linux/efi.h                     |   2 +
 9 files changed, 197 insertions(+), 155 deletions(-)
 create mode 100644 drivers/firmware/efi/runtime-wrappers.c

1.8.3.2

In order for other archs (such as arm64) to be able to reuse the virtual mode function call wrappers, move them to drivers/firmware/efi/runtime.c.

---
 arch/x86/Kconfig                        |   1 +
 arch/x86/platform/efi/efi.c             | 144 +---------------------------
 drivers/firmware/efi/Kconfig            |   7 ++
 drivers/firmware/efi/Makefile           |   1 +
 drivers/firmware/efi/runtime-wrappers.c | 161 ++++++++++++++++++++++++++++++++
 include/linux/efi.h                     |   2 +
 6 files changed, 174 insertions(+), 142 deletions(-)
 create mode 100644 drivers/firmware/efi/runtime-wrappers.c

index a8f749ef0fdc..4c3f026aa5ce 100644
@@ -1522,6 +1522,7 @@ config EFI
 	bool "EFI runtime service support"
 	depends on ACPI
 	select UCS2_STRING
+	select EFI_RUNTIME_WRAPPERS
 	---help---
 	  This enables the kernel to use EFI runtime services that are
 	  available (such as the EFI variable services).

index d420ae2d3413..04a7af46736a 100644
@@ -54,6 +54,13 @@ config EFI_PARAMS_FROM_FDT
 	  the EFI runtime support gets system table address, memory
           map address, and other parameters from the device tree.
 
+config EFI_RUNTIME_WRAPPERS
+	bool
+	help
+	  Selected by the arch if it needs to wrap UEFI Runtime Services calls,
+	  in which case it needs to provide #definitions of efi_call_virt and
+	  __efi_call_virt in <asm/efi.h>
+
 endmenu
 
 config UEFI_CPER

index 9553496b0f43..e1096539eedb 100644
@@ -6,3 +6,4 @@ obj-$(CONFIG_EFI_VARS)			+= efivars.o
 obj-$(CONFIG_EFI_VARS_PSTORE)		+= efi-pstore.o
 obj-$(CONFIG_UEFI_CPER)			+= cper.o
 obj-$(CONFIG_EFI_RUNTIME_MAP)		+= runtime-map.o
+obj-$(CONFIG_EFI_RUNTIME_WRAPPERS)	+= runtime-wrappers.o

index 41bbf8ba4ba8..0ceb816bdfc2 100644
@@ -521,6 +521,8 @@ typedef efi_status_t efi_query_capsule_caps_t(efi_capsule_header_t **capsules,
 					      int *reset_type);
 typedef efi_status_t efi_query_variable_store_t(u32 attributes, unsigned long size);
 
+void efi_native_runtime_setup(void);
+
 /*
  *  EFI Configuration Table and GUID definitions
  */

1.8.3.2

According to the UEFI spec section 2.3.6.4, the use of FP/SIMD instructions is allowed, and should adhere to the AAPCS64 calling convention, which states that 'only the bottom 64 bits of each value stored in registers v8-v15 need to be preserved' (section 5.1.2).

This applies equally to UEFI Runtime Services called by the kernel, so make sure the FP/SIMD register file is preserved in this case. We do this by enabling the wrappers for UEFI Runtime Services (CONFIG_EFI_RUNTIME_WRAPPERS) and inserting calls to kernel_neon_begin() and kernel_neon_end() into these wrappers.

---
 arch/arm64/Kconfig           |  1 +
 arch/arm64/include/asm/efi.h | 21 +++++++++++++++++++++
 arch/arm64/kernel/efi.c      | 14 +-------------
 3 files changed, 23 insertions(+), 13 deletions(-)

index a474de346be6..93e11f4d9513 100644
@@ -299,6 +299,7 @@ config EFI
 	select LIBFDT
 	select UCS2_STRING
 	select EFI_PARAMS_FROM_FDT
+	select EFI_RUNTIME_WRAPPERS
 	default y
 	help
 	  This option provides support for runtime services provided

index 5a46c4e7f539..375ba342dca6 100644
@@ -2,6 +2,7 @@
 #define _ASM_EFI_H
 
 #include <asm/io.h>
+#include <asm/neon.h>
 
 #ifdef CONFIG_EFI
 extern void efi_init(void);

@@ -11,4 +12,24 @@ extern void efi_idmap_init(void);
 #define efi_idmap_init()
 #endif
 
+#define efi_call_virt(f, ...)						\
+({									\
+	efi_##f##_t *__f = efi.systab->runtime->f;			\
+	efi_status_t __s;						\
+									\
+	kernel_neon_begin();						\
+	__s = __f(__VA_ARGS__);						\
+	kernel_neon_end();						\
+	__s;								\
+})
+
+#define __efi_call_virt(f, ...)						\
+({									\
+	efi_##f##_t *__f = efi.systab->runtime->f;			\
+									\
+	kernel_neon_begin();						\
+	__f(__VA_ARGS__);						\
+	kernel_neon_end();						\
+})
+
 #endif /* _ASM_EFI_H */

index 14db1f6e8d7f..56c3327bbf79 100644
@@ -449,19 +449,7 @@ static int __init arm64_enter_virtual_mode(void)
 
 	/* Set up runtime services function pointers */
 	runtime = efi.systab->runtime;
-	efi.get_time = runtime->get_time;
-	efi.set_time = runtime->set_time;
-	efi.get_wakeup_time = runtime->get_wakeup_time;
-	efi.set_wakeup_time = runtime->set_wakeup_time;
-	efi.get_variable = runtime->get_variable;
-	efi.get_next_variable = runtime->get_next_variable;
-	efi.set_variable = runtime->set_variable;
-	efi.query_variable_info = runtime->query_variable_info;
-	efi.update_capsule = runtime->update_capsule;
-	efi.query_capsule_caps = runtime->query_capsule_caps;
-	efi.get_next_high_mono_count = runtime->get_next_high_mono_count;
-	efi.reset_system = runtime->reset_system;
-
+	efi_native_runtime_setup();
 	set_bit(EFI_RUNTIME_SERVICES, &efi.flags);
 
 	return 0;

1.8.3.2

Thanks Ard, applied.

FYI that "please queue up for 3.17" message is super helpful when I'm trying to figure out what branch to apply this to.

Matt Fleming, Intel Open Source Technology Center