[PATCH v2] arm64/sme: Fix EFI save/restore

[Mark Brown]

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: e0838f6373e5 ("arm64/sme: Save and restore streaming mode over EFI runtime calls")
Reported-by: kernel test robot <lkp at intel.com>
Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>
Signed-off-by: Mark Brown <broonie at kernel.org>
---

Still not tested, that won't happen till next week.

v2:
 - Add comments saying when we need to save/restore FFR.

 arch/arm64/kernel/fpsimd.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 819979398127..b93985a33bed 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/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;
 				}
 			}
 
-- 
2.30.2