On Fri, Feb 16, 2018 at 06:39:30PM +0000, Dave Martin wrote:
> Oops, forgot to post this patch that goes before patch 1 in the series.
>
> --8<--
>
> Expose an interface for associating an FPSIMD context with a CPU and
> checking the association, for use by KVM.
>
> Signed-off-by: Dave Martin <dave.mar...@arm.com>
> ---
> arch/arm64/include/asm/fpsimd.h | 5 +++++
> arch/arm64/kernel/fpsimd.c | 42
> +++++++++++++++++++++++++++++------------
> 2 files changed, 35 insertions(+), 12 deletions(-)
>
> diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
> index 8857a0f..f4ce4d6 100644
> --- a/arch/arm64/include/asm/fpsimd.h
> +++ b/arch/arm64/include/asm/fpsimd.h
> @@ -23,6 +23,7 @@
>
> #include <linux/cache.h>
> #include <linux/stddef.h>
> +#include <linux/types.h>
>
> /*
> * FP/SIMD storage area has:
> @@ -62,6 +63,8 @@ struct fpsimd_state {
>
> struct task_struct;
>
> +extern bool fpsimd_foreign_fpstate(struct fpsimd_state const *state);
> +
> extern void fpsimd_save_state(struct fpsimd_state *state);
> extern void fpsimd_load_state(struct fpsimd_state *state);
>
> @@ -76,6 +79,8 @@ extern void fpsimd_update_current_state(struct
> user_fpsimd_state const *state);
> extern void fpsimd_flush_task_state(struct task_struct *target);
> extern void sve_flush_cpu_state(void);
>
> +extern void fpsimd_bind_state_to_cpu(struct fpsimd_state *state);
> +
> /* Maximum VL that SVE VL-agnostic software can transparently support */
> #define SVE_VL_ARCH_MAX 0x100
>
> diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
> index e7226c4..138efaf 100644
> --- a/arch/arm64/kernel/fpsimd.c
> +++ b/arch/arm64/kernel/fpsimd.c
> @@ -38,6 +38,7 @@
> #include <linux/signal.h>
> #include <linux/slab.h>
> #include <linux/sysctl.h>
> +#include <linux/types.h>
>
> #include <asm/fpsimd.h>
> #include <asm/cputype.h>
> @@ -121,6 +122,14 @@ struct fpsimd_last_state_struct {
>
> static DEFINE_PER_CPU(struct fpsimd_last_state_struct, fpsimd_last_state);
>
> +bool fpsimd_foreign_fpstate(struct fpsimd_state const *st)
> +{
> + WARN_ON(!in_softirq() && !irqs_disabled());
> +
> + return st->cpu != smp_processor_id() ||
> + st != __this_cpu_read(fpsimd_last_state.st);
> +}
> +
> /* Default VL for tasks that don't set it explicitly: */
> static int sve_default_vl = -1;
>
> @@ -908,13 +917,10 @@ void fpsimd_thread_switch(struct task_struct *next)
> * the TIF_FOREIGN_FPSTATE flag so the state will be loaded
> * upon the next return to userland.
> */
> - struct fpsimd_state *st = &next->thread.fpsimd_state;
> -
> - if (__this_cpu_read(fpsimd_last_state.st) == st
> - && st->cpu == smp_processor_id())
> - clear_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE);
> - else
> + if (fpsimd_foreign_fpstate(¤t->thread.fpsimd_state))
> set_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE);
> + else
> + clear_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE);
> }
> }
>
> @@ -996,19 +1002,31 @@ void fpsimd_signal_preserve_current_state(void)
> sve_to_fpsimd(current);
> }
>
> +static void __fpsimd_bind_to_cpu(struct fpsimd_last_state_struct *last,
> + struct fpsimd_state *st)
> +{
> + WARN_ON(!in_softirq() || !irqs_disabled());
You meant && here, right?
Currently this makes my box explode.
Thanks,
-Christoffer
> +
> + last->st = st;
> + st->cpu = smp_processor_id();
> +}
> +
> +void fpsimd_bind_state_to_cpu(struct fpsimd_state *st)
> +{
> + __fpsimd_bind_to_cpu(this_cpu_ptr(&fpsimd_last_state), st);
> +}
> +
> /*
> * Associate current's FPSIMD context with this cpu
> * Preemption must be disabled when calling this function.
> */
> -static void fpsimd_bind_to_cpu(void)
> +static void fpsimd_bind_task_to_cpu(void)
> {
> struct fpsimd_last_state_struct *last =
> this_cpu_ptr(&fpsimd_last_state);
> - struct fpsimd_state *st = ¤t->thread.fpsimd_state;
>
> - last->st = st;
> + __fpsimd_bind_to_cpu(last, ¤t->thread.fpsimd_state);
> last->sve_in_use = test_thread_flag(TIF_SVE);
> - st->cpu = smp_processor_id();
> }
>
> /*
> @@ -1025,7 +1043,7 @@ void fpsimd_restore_current_state(void)
>
> if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
> task_fpsimd_load();
> - fpsimd_bind_to_cpu();
> + fpsimd_bind_task_to_cpu();
> }
>
> local_bh_enable();
> @@ -1050,7 +1068,7 @@ void fpsimd_update_current_state(struct
> user_fpsimd_state const *state)
> task_fpsimd_load();
>
> if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE))
> - fpsimd_bind_to_cpu();
> + fpsimd_bind_task_to_cpu();
>
> local_bh_enable();
> }
> --
> 2.1.4
>
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