Re: [PATCH v9 04/30] arm64/fpsimd: Check enable bit for FA64 when saving EFI state
From: Fuad Tabba <tabba@google.com>
Date: 2026-01-07 19:25:54
Also in:
kvm, kvmarm, linux-doc, linux-kselftest, lkml
On Tue, 23 Dec 2025 at 01:21, Mark Brown [off-list ref] wrote:
Currently when deciding if we need to save FFR when in streaming mode prior to EFI calls we check if FA64 is supported by the system. Since KVM guest support will mean that FA64 might be enabled and disabled at runtime switch to checking if traps for FA64 are enabled in SMCR_EL1 instead. Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Fuad Tabba <tabba@google.com> Cheers, /fuad
quoted hunk ↗ jump to hunk
--- arch/arm64/kernel/fpsimd.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 887fce177c92..f4e8cee00198 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c@@ -1948,6 +1948,11 @@ static bool efi_sm_state; * either doing something wrong or you need to propose some refactoring. */ +static bool fa64_enabled(void) +{ + return read_sysreg_s(SYS_SMCR_EL1) & SMCR_ELx_FA64; +} + /* * __efi_fpsimd_begin(): prepare FPSIMD for making an EFI runtime services call */@@ -1980,7 +1985,7 @@ void __efi_fpsimd_begin(void) * Unless we have FA64 FFR does not * exist in streaming mode. */ - if (!system_supports_fa64()) + if (!fa64_enabled()) ffr = !(svcr & SVCR_SM_MASK); }@@ -2028,7 +2033,7 @@ void __efi_fpsimd_end(void) * Unless we have FA64 FFR does not * exist in streaming mode. */ - if (!system_supports_fa64()) + if (!fa64_enabled()) ffr = false; } } --2.47.3