arm64/sme: Fix EFI save/restore

The EFI save/restore code is confused. When saving the check for saving
FFR is inverted due to confusion with the streaming mode check, and when
restoring we check if we need to restore FFR by checking the percpu
efi_sm_state without the required wrapper rather than based on the
combination of FA64 support and streaming mode.

Fixes: e0838f63 ("arm64/sme: Save and restore streaming mode over EFI runtime calls")
Reported-by: Nkernel test robot <lkp@intel.com>
Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220602124132.3528951-1-broonie@kernel.orgSigned-off-by: NCatalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/fpsimd.c

@@ -1916,10 +1916,15 @@ void __efi_fpsimd_begin(void)
 			if (system_supports_sme()) {
 				svcr = read_sysreg_s(SYS_SVCR);
 
-				if (!system_supports_fa64())
-					ffr = svcr & SVCR_SM_MASK;
+				__this_cpu_write(efi_sm_state,
+						 svcr & SVCR_SM_MASK);
 
-				__this_cpu_write(efi_sm_state, ffr);
+				/*
+				 * Unless we have FA64 FFR does not
+				 * exist in streaming mode.
+				 */
+				if (!system_supports_fa64())
+					ffr = !(svcr & SVCR_SM_MASK);
 			}
 
 			sve_save_state(sve_state + sve_ffr_offset(sve_max_vl()),
@@ -1964,8 +1969,13 @@ void __efi_fpsimd_end(void)
 					sysreg_clear_set_s(SYS_SVCR,
 							   0,
 							   SVCR_SM_MASK);
+
+					/*
+					 * Unless we have FA64 FFR does not
+					 * exist in streaming mode.
+					 */
 					if (!system_supports_fa64())
-						ffr = efi_sm_state;
+						ffr = false;
 				}
 			}