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Commit d1797615 authored by Dave Martin's avatar Dave Martin Committed by Marc Zyngier
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arm64: fpsimd: Generalise context saving for non-task contexts 



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: default avatarDave Martin <Dave.Martin@arm.com>
Reviewed-by: default avatarAlex Bennée <alex.bennee@linaro.org>
Acked-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
parent ceda9fff

arch/arm64/kernel/fpsimd.c

+14 −12
Original line number Diff line number Diff line
@@ -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: