efi/x86: Simplify 64-bit EFI firmware call wrapper

The efi_call() wrapper used to invoke EFI runtime services serves
a number of purposes:
- realign the stack to 16 bytes
- preserve FP and CR0 register state
- translate from SysV to MS calling convention.

Preserving CR0.TS is no longer necessary in Linux, and preserving the
FP register state is also redundant in most cases, since efi_call() is
almost always used from within the scope of a pair of kernel_fpu_begin()/
kernel_fpu_end() calls, with the exception of the early call to
SetVirtualAddressMap() and the SGI UV support code.

So let's add a pair of kernel_fpu_begin()/_end() calls there as well,
and remove the unnecessary code from the assembly implementation of
efi_call(), and only keep the pieces that deal with the stack
alignment and the ABI translation.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Matthew Garrett <mjg59@google.com>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20200103113953.9571-10-ardb@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index a7f11d1ff7c4..03565dad0c4b 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -1019,6 +1019,8 @@ efi_status_t __init efi_set_virtual_address_map(unsigned long memory_map_size,
 		efi_switch_mm(&efi_mm);
 	}
 
+	kernel_fpu_begin();
+
 	/* Disable interrupts around EFI calls: */
 	local_irq_save(flags);
 	status = efi_call(efi.systab->runtime->set_virtual_address_map,
@@ -1026,6 +1028,7 @@ efi_status_t __init efi_set_virtual_address_map(unsigned long memory_map_size,
 			  descriptor_version, virtual_map);
 	local_irq_restore(flags);
 
+	kernel_fpu_end();
 
 	if (save_pgd)
 		efi_old_memmap_phys_epilog(save_pgd);