Merge tag 'x86_fpu_for_v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 FPU updates from Borislav Petkov:
 "x86 fpu usage optimization and cleanups:

   - make 64-bit kernel code which uses 387 insns request a x87 init
     (FNINIT) explicitly when using the FPU

   - misc cleanups"

* tag 'x86_fpu_for_v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/fpu/xstate: Use sizeof() instead of a constant
  x86/fpu/64: Don't FNINIT in kernel_fpu_begin()
  x86/fpu: Make the EFI FPU calling convention explicit

1 files changed, 20 insertions, 4 deletions

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 627347af343a..4d0b126835b8 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -69,17 +69,33 @@ extern unsigned long efi_mixed_mode_stack_pa;
 		#f " called with too many arguments (" #p ">" #n ")");	\
 })
 
+static inline void efi_fpu_begin(void)
+{
+	/*
+	 * The UEFI calling convention (UEFI spec 2.3.2 and 2.3.4) requires
+	 * that FCW and MXCSR (64-bit) must be initialized prior to calling
+	 * UEFI code.  (Oddly the spec does not require that the FPU stack
+	 * be empty.)
+	 */
+	kernel_fpu_begin_mask(KFPU_387 | KFPU_MXCSR);
+}
+
+static inline void efi_fpu_end(void)
+{
+	kernel_fpu_end();
+}
+
 #ifdef CONFIG_X86_32
 #define arch_efi_call_virt_setup()					\
 ({									\
-	kernel_fpu_begin();						\
+	efi_fpu_begin();						\
 	firmware_restrict_branch_speculation_start();			\
 })
 
 #define arch_efi_call_virt_teardown()					\
 ({									\
 	firmware_restrict_branch_speculation_end();			\
-	kernel_fpu_end();						\
+	efi_fpu_end();							\
 })
 
 #define arch_efi_call_virt(p, f, args...)	p->f(args)
@@ -98,7 +114,7 @@ extern asmlinkage u64 __efi_call(void *fp, ...);
 #define arch_efi_call_virt_setup()					\
 ({									\
 	efi_sync_low_kernel_mappings();					\
-	kernel_fpu_begin();						\
+	efi_fpu_begin();						\
 	firmware_restrict_branch_speculation_start();			\
 	efi_enter_mm();							\
 })
@@ -110,7 +126,7 @@ extern asmlinkage u64 __efi_call(void *fp, ...);
 ({									\
 	efi_leave_mm();							\
 	firmware_restrict_branch_speculation_end();			\
-	kernel_fpu_end();						\
+	efi_fpu_end();							\
 })
 
 #ifdef CONFIG_KASAN