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From:   Mark Brown <broonie@kernel.org>
Date:   Thu, 03 Aug 2023 01:19:06 +0100
Subject: [PATCH] arm64/ptrace: Flush FP state when setting ZT0
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Message-Id: <20230803-arm64-fix-ptrace-zt0-flush-v1-1-72e854eaf96e@kernel.org>
To:     Oleg Nesterov <oleg@redhat.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>
Cc:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Mark Brown <broonie@kernel.org>, stable@vger.kernel.org
Precedence: bulk

When setting ZT0 via ptrace we do not currently force a reload of the
floating point register state from memory, do that to ensure that the newly
set value gets loaded into the registers on next task execution.

The function was templated off the function for FPSIMD which due to our
providing the option of embedding a FPSIMD regset within the SVE regset
does not directly include the flush.

Fixes: f90b529bcbe5 ("arm64/sme: Implement ZT0 ptrace support")
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org
---
 arch/arm64/kernel/ptrace.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index d7f4f0d1ae12..740e81e9db04 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -1180,6 +1180,8 @@ static int zt_set(struct task_struct *target,
 	if (ret == 0)
 		target->thread.svcr |= SVCR_ZA_MASK;
 
+	fpsimd_flush_task_state(target);
+
 	return ret;
 }
 

---
base-commit: 5d0c230f1de8c7515b6567d9afba1f196fb4e2f4
change-id: 20230802-arm64-fix-ptrace-zt0-flush-d6d71b9f8461

Best regards,
-- 
Mark Brown <broonie@kernel.org>