From 2f856c214d481a27e4ee45dbee33b82430330cf1 Mon Sep 17 00:00:00 2001
From: Dave Martin <Dave.Martin@arm.com>
Date: Tue, 31 Oct 2017 15:51:11 +0000
Subject: [PATCH] arm64/sve: Preserve SVE registers around kernel-mode NEON use
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Git-commit: 1bd3f93641ec710015fcb3badca07dacd58c91d3
Patch-mainline: v4.15-rc1
References: fate#325866

Kernel-mode NEON will corrupt the SVE vector registers, due to the
way they alias the FPSIMD vector registers in the hardware.

This patch ensures that any live SVE register content for the task
is saved by kernel_neon_begin().  The data will be restored in the
usual way on return to userspace.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
 arch/arm64/kernel/fpsimd.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index ad718419e1fe..4d146707a2db 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -885,8 +885,10 @@ void kernel_neon_begin(void)
 	__this_cpu_write(kernel_neon_busy, true);
 
 	/* Save unsaved task fpsimd state, if any: */
-	if (current->mm && !test_and_set_thread_flag(TIF_FOREIGN_FPSTATE))
-		fpsimd_save_state(&current->thread.fpsimd_state);
+	if (current->mm) {
+		task_fpsimd_save();
+		set_thread_flag(TIF_FOREIGN_FPSTATE);
+	}
 
 	/* Invalidate any task state remaining in the fpsimd regs: */
 	__this_cpu_write(fpsimd_last_state, NULL);
-- 
2.11.0