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author | Dave Martin <Dave.Martin@arm.com> | 2018-05-09 14:27:41 +0100 |
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committer | Marc Zyngier <marc.zyngier@arm.com> | 2018-05-25 12:27:56 +0100 |
commit | 0cff8e776f8f58f494ed16b28baf209c1b73b079 (patch) | |
tree | fc2957da4897764e303398a235830862c9488244 /arch/arm64/kernel/fpsimd.c | |
parent | df3fb96820455ef70a51630d1be336d4f2602111 (diff) | |
download | op-kernel-dev-0cff8e776f8f58f494ed16b28baf209c1b73b079.zip op-kernel-dev-0cff8e776f8f58f494ed16b28baf209c1b73b079.tar.gz |
arm64/sve: Refactor user SVE trap maintenance for external use
In preparation for optimising the way KVM manages switching the
guest and host FPSIMD state, it is necessary to provide a means for
code outside arch/arm64/kernel/fpsimd.c to restore the user trap
configuration for SVE correctly for the current task.
Rather than requiring external code to duplicate the maintenance
explicitly, this patch moves the trap maintenenace to
fpsimd_bind_to_cpu(), since it is logically part of the work of
associating the current task with the cpu.
Because fpsimd_bind_to_cpu() is rather a cryptic name to publish
alongside fpsimd_bind_state_to_cpu(), the former function is
renamed to fpsimd_bind_task_to_cpu() to make its purpose more
explicit.
This patch makes appropriate changes to ensure that
fpsimd_bind_task_to_cpu() is always called alongside
task_fpsimd_load(), so that the trap maintenance continues to be
done in every situation where it was done prior to this patch.
As a side-effect, the metadata updates done by
fpsimd_bind_task_to_cpu() now change from conditional to
unconditional in the "already bound" case of sigreturn. This is
harmless, and a couple of extra stores on this slow path will not
impact performance. I consider this a reasonable price to pay for
a slightly cleaner interface.
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Diffstat (limited to 'arch/arm64/kernel/fpsimd.c')
-rw-r--r-- | arch/arm64/kernel/fpsimd.c | 30 |
1 files changed, 15 insertions, 15 deletions
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index d736b6c..d5f659f 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -257,16 +257,6 @@ static void task_fpsimd_load(void) sve_vq_from_vl(current->thread.sve_vl) - 1); else fpsimd_load_state(¤t->thread.uw.fpsimd_state); - - if (system_supports_sve()) { - /* Toggle SVE trapping for userspace if needed */ - if (test_thread_flag(TIF_SVE)) - sve_user_enable(); - else - sve_user_disable(); - - /* Serialised by exception return to user */ - } } /* @@ -278,7 +268,7 @@ static void task_fpsimd_load(void) static void fpsimd_save(void) { struct user_fpsimd_state *st = __this_cpu_read(fpsimd_last_state.st); - /* set by fpsimd_bind_to_cpu() */ + /* set by fpsimd_bind_task_to_cpu() */ WARN_ON(!in_softirq() && !irqs_disabled()); @@ -996,7 +986,7 @@ void fpsimd_signal_preserve_current_state(void) * 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); @@ -1004,6 +994,16 @@ static void fpsimd_bind_to_cpu(void) last->st = ¤t->thread.uw.fpsimd_state; last->sve_in_use = test_thread_flag(TIF_SVE); current->thread.fpsimd_cpu = smp_processor_id(); + + if (system_supports_sve()) { + /* Toggle SVE trapping for userspace if needed */ + if (test_thread_flag(TIF_SVE)) + sve_user_enable(); + else + sve_user_disable(); + + /* Serialised by exception return to user */ + } } /* @@ -1020,7 +1020,7 @@ 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(); @@ -1043,9 +1043,9 @@ void fpsimd_update_current_state(struct user_fpsimd_state const *state) fpsimd_to_sve(current); task_fpsimd_load(); + fpsimd_bind_task_to_cpu(); - if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) - fpsimd_bind_to_cpu(); + clear_thread_flag(TIF_FOREIGN_FPSTATE); local_bh_enable(); } |