[PATCH v3 2/2] efi/arm64: preserve FP/SIMD registers on UEFI runtime services calls

[Ard Biesheuvel]

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.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
Acked-by: Catalin Marinas <catalin.marinas at arm.com>
---
 arch/arm64/Kconfig           |  1 +
 arch/arm64/include/asm/efi.h | 21 +++++++++++++++++++++
 arch/arm64/kernel/efi.c      | 14 +-------------
 3 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index a474de346be6..93e11f4d9513 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -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
diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index 5a46c4e7f539..375ba342dca6 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -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 */
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index 14db1f6e8d7f..56c3327bbf79 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -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