diff options
| -rw-r--r-- | arch/arm64/include/asm/fpsimd.h | 3 | ||||
| -rw-r--r-- | arch/arm64/kernel/entry-common.c | 46 | ||||
| -rw-r--r-- | arch/arm64/kernel/fpsimd.c | 15 |
3 files changed, 47 insertions, 17 deletions
diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h index b7adb2c72204..11b9c6a5e037 100644 --- a/arch/arm64/include/asm/fpsimd.h +++ b/arch/arm64/include/asm/fpsimd.h @@ -6,6 +6,7 @@ #define __ASM_FP_H #include <asm/errno.h> +#include <asm/percpu.h> #include <asm/ptrace.h> #include <asm/processor.h> #include <asm/sigcontext.h> @@ -92,6 +93,8 @@ struct cpu_fp_state { enum fp_type to_save; }; +DECLARE_PER_CPU(struct cpu_fp_state, fpsimd_last_state); + extern void fpsimd_bind_state_to_cpu(struct cpu_fp_state *fp_state); extern void fpsimd_flush_task_state(struct task_struct *target); diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c index b260ddc4d3e9..fa8a090339e2 100644 --- a/arch/arm64/kernel/entry-common.c +++ b/arch/arm64/kernel/entry-common.c @@ -393,20 +393,16 @@ static bool cortex_a76_erratum_1463225_debug_handler(struct pt_regs *regs) * As per the ABI exit SME streaming mode and clear the SVE state not * shared with FPSIMD on syscall entry. */ -static inline void fp_user_discard(void) +static inline void fpsimd_syscall_enter(void) { - /* - * If SME is active then exit streaming mode. If ZA is active - * then flush the SVE registers but leave userspace access to - * both SVE and SME enabled, otherwise disable SME for the - * task and fall through to disabling SVE too. This means - * that after a syscall we never have any streaming mode - * register state to track, if this changes the KVM code will - * need updating. - */ + /* Ensure PSTATE.SM is clear, but leave PSTATE.ZA as-is. */ if (system_supports_sme()) sme_smstop_sm(); + /* + * The CPU is not in streaming mode. If non-streaming SVE is not + * supported, there is no SVE state that needs to be discarded. + */ if (!system_supports_sve()) return; @@ -416,6 +412,33 @@ static inline void fp_user_discard(void) sve_vq_minus_one = sve_vq_from_vl(task_get_sve_vl(current)) - 1; sve_flush_live(true, sve_vq_minus_one); } + + /* + * Any live non-FPSIMD SVE state has been zeroed. Allow + * fpsimd_save_user_state() to lazily discard SVE state until either + * the live state is unbound or fpsimd_syscall_exit() is called. + */ + __this_cpu_write(fpsimd_last_state.to_save, FP_STATE_FPSIMD); +} + +static __always_inline void fpsimd_syscall_exit(void) +{ + if (!system_supports_sve()) + return; + + /* + * The current task's user FPSIMD/SVE/SME state is now bound to this + * CPU. The fpsimd_last_state.to_save value is either: + * + * - FP_STATE_FPSIMD, if the state has not been reloaded on this CPU + * since fpsimd_syscall_enter(). + * + * - FP_STATE_CURRENT, if the state has been reloaded on this CPU at + * any point. + * + * Reset this to FP_STATE_CURRENT to stop lazy discarding. + */ + __this_cpu_write(fpsimd_last_state.to_save, FP_STATE_CURRENT); } UNHANDLED(el1t, 64, sync) @@ -739,10 +762,11 @@ static void noinstr el0_svc(struct pt_regs *regs) { enter_from_user_mode(regs); cortex_a76_erratum_1463225_svc_handler(); - fp_user_discard(); + fpsimd_syscall_enter(); local_daif_restore(DAIF_PROCCTX); do_el0_svc(regs); exit_to_user_mode(regs); + fpsimd_syscall_exit(); } static void noinstr el0_fpac(struct pt_regs *regs, unsigned long esr) diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 422b9d43b1e6..9f1890d692df 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -119,7 +119,7 @@ * whatever is in the FPSIMD registers is not saved to memory, but discarded. */ -static DEFINE_PER_CPU(struct cpu_fp_state, fpsimd_last_state); +DEFINE_PER_CPU(struct cpu_fp_state, fpsimd_last_state); __ro_after_init struct vl_info vl_info[ARM64_VEC_MAX] = { #ifdef CONFIG_ARM64_SVE @@ -451,12 +451,15 @@ static void fpsimd_save_user_state(void) *(last->fpmr) = read_sysreg_s(SYS_FPMR); /* - * If a task is in a syscall the ABI allows us to only - * preserve the state shared with FPSIMD so don't bother - * saving the full SVE state in that case. + * Save SVE state if it is live. + * + * The syscall ABI discards live SVE state at syscall entry. When + * entering a syscall, fpsimd_syscall_enter() sets to_save to + * FP_STATE_FPSIMD to allow the SVE state to be lazily discarded until + * either new SVE state is loaded+bound or fpsimd_syscall_exit() is + * called prior to a return to userspace. */ - if ((last->to_save == FP_STATE_CURRENT && test_thread_flag(TIF_SVE) && - !in_syscall(current_pt_regs())) || + if ((last->to_save == FP_STATE_CURRENT && test_thread_flag(TIF_SVE)) || last->to_save == FP_STATE_SVE) { save_sve_regs = true; save_ffr = true; |