x86/efi: Save and restore FPU context around efi_calls (x86_64)

Do a complete FPU context save/restore around the EFI calls. This required
as runtime EFI firmware may potentially use the FPU.

This change covers only the x86_64 configuration.

Signed-off-by: Ricardo Neri <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Signed-off-by: Matt Fleming <[e-mail]>

arch/x86/include/asm/efi.h

···
 #ifndef _ASM_X86_EFI_H
 #define _ASM_X86_EFI_H
 
+#include <asm/i387.h>
 /*
  * We map the EFI regions needed for runtime services non-contiguously,
  * with preserved alignment on virtual addresses starting from -4G down
···
 									\
 	efi_sync_low_kernel_mappings();					\
 	preempt_disable();						\
+	__kernel_fpu_begin();						\
 	__s = efi_call((void *)efi.systab->runtime->f, __VA_ARGS__);	\
+	__kernel_fpu_end();						\
 	preempt_enable();						\
 	__s;								\
 })