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arm64: fpsimd: Generalise context saving for non-task contexts

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In preparation for allowing non-task (i.e., KVM vcpu) FPSIMD
contexts to be handled by the fpsimd common code, this patch adapts
task_fpsimd_save() to save back the currently loaded context,
removing the explicit dependency on current.

The relevant storage to write back to in memory is now found by
examining the fpsimd_last_state percpu struct.

fpsimd_save() does nothing unless TIF_FOREIGN_FPSTATE is clear, and
fpsimd_last_state is updated under local_bh_disable() or
local_irq_disable() everywhere that TIF_FOREIGN_FPSTATE is cleared:
thus, fpsimd_save() will write back to the correct storage for the
loaded context.

No functional change.

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>
This commit is contained in:
Dave Martin 2018-04-06 14:55:59 +01:00 committed by Marc Zyngier
parent ceda9fff70
commit d179761519
1 changed files with 14 additions and 12 deletions
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26
arch/arm64/kernel/fpsimd.c
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@ -270,13 +270,16 @@ static void task_fpsimd_load(void)
}
/*
* Ensure current's FPSIMD/SVE storage in thread_struct is up to date
* with respect to the CPU registers.
* Ensure FPSIMD/SVE storage in memory for the loaded context is up to
* date with respect to the CPU registers.
*
* Softirqs (and preemption) must be disabled.
*/
static void task_fpsimd_save(void)
static void fpsimd_save(void)
{
struct user_fpsimd_state *st = __this_cpu_read(fpsimd_last_state.st);
/* set by fpsimd_bind_to_cpu() */
WARN_ON(!in_softirq() && !irqs_disabled());
if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
@ -291,10 +294,9 @@ static void task_fpsimd_save(void)
return;
}
sve_save_state(sve_pffr(current),
&current->thread.uw.fpsimd_state.fpsr);
sve_save_state(sve_pffr(current), &st->fpsr);
} else
fpsimd_save_state(&current->thread.uw.fpsimd_state);
fpsimd_save_state(st);
}
}
@ -598,7 +600,7 @@ int sve_set_vector_length(struct task_struct *task,
if (task == current) {
local_bh_disable();
task_fpsimd_save();
fpsimd_save();
set_thread_flag(TIF_FOREIGN_FPSTATE);
}
@ -837,7 +839,7 @@ asmlinkage void do_sve_acc(unsigned int esr, struct pt_regs *regs)
local_bh_disable();
task_fpsimd_save();
fpsimd_save();
fpsimd_to_sve(current);
/* Force ret_to_user to reload the registers: */
@ -898,7 +900,7 @@ void fpsimd_thread_switch(struct task_struct *next)
* 'current'.
*/
if (current->mm)
task_fpsimd_save();
fpsimd_save();
if (next->mm) {
/*
@ -980,7 +982,7 @@ void fpsimd_preserve_current_state(void)
return;
local_bh_disable();
task_fpsimd_save();
fpsimd_save();
local_bh_enable();
}
@ -1121,7 +1123,7 @@ void kernel_neon_begin(void)
/* Save unsaved task fpsimd state, if any: */
if (current->mm)
task_fpsimd_save();
fpsimd_save();
/* Invalidate any task state remaining in the fpsimd regs: */
fpsimd_flush_cpu_state();
@ -1244,7 +1246,7 @@ static int fpsimd_cpu_pm_notifier(struct notifier_block *self,
switch (cmd) {
case CPU_PM_ENTER:
if (current->mm)
task_fpsimd_save();
fpsimd_save();
fpsimd_flush_cpu_state();
break;
case CPU_PM_EXIT: