[{"id":1768504,"web_url":"http://patchwork.ozlabs.org/comment/1768504/","msgid":"<87efr9a6xl.fsf@linaro.org>","list_archive_url":null,"date":"2017-09-14T10:52:22","subject":"Re: [PATCH v2 17/28] arm64/sve: Preserve SVE registers around\n\tkernel-mode NEON use","submitter":{"id":39532,"url":"http://patchwork.ozlabs.org/api/people/39532/","name":"Alex Bennée","email":"alex.bennee@linaro.org"},"content":"Dave Martin writes:\n\n> Kernel-mode NEON will corrupt the SVE vector registers, due to the\n> way they alias the FPSIMD vector registers in the hardware.\n>\n> This patch ensures that any live SVE register content for the task\n> is saved by kernel_neon_begin(). The data will be restored in the\n> usual way on return to userspace.\n>\n> Signed-off-by: Dave Martin \n> Reviewed-by: Ard Biesheuvel \n\nReviewed-by: Alex Bennée \n\n> ---\n> arch/arm64/kernel/fpsimd.c | 6 ++++--\n> 1 file changed, 4 insertions(+), 2 deletions(-)\n>\n> diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c\n> index cea05a7..dd89acf 100644\n> --- a/arch/arm64/kernel/fpsimd.c\n> +++ b/arch/arm64/kernel/fpsimd.c\n> @@ -744,8 +744,10 @@ void kernel_neon_begin(void)\n> \t__this_cpu_write(kernel_neon_busy, true);\n>\n> \t/* Save unsaved task fpsimd state, if any: */\n> -\tif (current->mm && !test_and_set_thread_flag(TIF_FOREIGN_FPSTATE))\n> -\t\tfpsimd_save_state(¤t->thread.fpsimd_state);\n> +\tif (current->mm) {\n> +\t\ttask_fpsimd_save();\n> +\t\tset_thread_flag(TIF_FOREIGN_FPSTATE);\n> +\t}\n>\n> \t/* Invalidate any task state remaining in the fpsimd regs: */\n> \t__this_cpu_write(fpsimd_last_state, NULL);\n\n\n--\nAlex Bennée","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":["patchwork-incoming@bilbo.ozlabs.org","mailing list libc-alpha@sourceware.org"],"Authentication-Results":["ozlabs.org;\n\tspf=pass (mailfrom) smtp.mailfrom=sourceware.org\n\t(client-ip=209.132.180.131; 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emacs 25.2.50.3","From":"Alex =?utf-8?q?Benn=C3=A9e?= ","To":"Dave Martin ","Cc":"linux-arm-kernel@lists.infradead.org,\n\tCatalin Marinas ,\n\tWill Deacon ,\n\tArd Biesheuvel ,\n\tSzabolcs Nagy ,\n\tRichard Sandiford ,\n\tkvmarm@lists.cs.columbia.edu, libc-alpha@sourceware.org,\n\tlinux-arch@vger.kernel.org","Subject":"Re: [PATCH v2 17/28] arm64/sve: Preserve SVE registers around\n\tkernel-mode NEON use","In-reply-to":"<1504198860-12951-18-git-send-email-Dave.Martin@arm.com>","Date":"Thu, 14 Sep 2017 11:52:22 +0100","Message-ID":"<87efr9a6xl.fsf@linaro.org>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Transfer-Encoding":"8bit"}}]