Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935276AbeAHQ4s (ORCPT + 1 other); Mon, 8 Jan 2018 11:56:48 -0500 Received: from ozlabs.org ([103.22.144.67]:58069 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757460AbeAHQzw (ORCPT ); Mon, 8 Jan 2018 11:55:52 -0500 From: Michael Ellerman To: linuxppc-dev@ozlabs.org Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, peterz@infradead.org, npiggin@gmail.com, anton@samba.org, mikey@neuling.org, oohall@gmail.com, paulus@samba.org Subject: [PATCH 08/11] powerpc/64s: Support disabling RFI flush with no_rfi_flush and nopti Date: Tue, 9 Jan 2018 03:54:50 +1100 Message-Id: <20180108165453.26066-8-mpe@ellerman.id.au> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180108165453.26066-1-mpe@ellerman.id.au> References: <20180108165453.26066-1-mpe@ellerman.id.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: Because there may be some performance overhead of the RFI flush, add kernel command line options to disable it. We add a sensibly named 'no_rfi_flush' option, but we also hijack the x86 option 'nopti'. The RFI flush is not the same as KPTI, but if we see 'nopti' we can guess that the user is trying to avoid any overhead of Meltdown mitigations, and it means we don't have to educate every one about a different command line option. Signed-off-by: Michael Ellerman --- arch/powerpc/kernel/setup_64.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index d26b11816b8f..8f90b0b4f5ac 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -803,8 +803,29 @@ early_initcall(disable_hardlockup_detector); #ifdef CONFIG_PPC_BOOK3S_64 static enum l1d_flush_type enabled_flush_types; static void *l1d_flush_fallback_area; +static bool no_rfi_flush; bool rfi_flush; +static int __init handle_no_rfi_flush(char *p) +{ + pr_info("rfi-flush: disabled on command line."); + no_rfi_flush = true; + return 0; +} +early_param("no_rfi_flush", handle_no_rfi_flush); + +/* + * The RFI flush is not KPTI, but because users will see doco that says to use + * nopti we hijack that option here to also disable the RFI flush. + */ +static int __init handle_no_pti(char *p) +{ + pr_info("rfi-flush: disabling due to 'nopti' on command line.\n"); + handle_no_rfi_flush(NULL); + return 0; +} +early_param("nopti", handle_no_pti); + static void do_nothing(void *unused) { /* @@ -871,6 +892,7 @@ void __init setup_rfi_flush(enum l1d_flush_type types, bool enable) enabled_flush_types = types; - rfi_flush_enable(enable); + if (!no_rfi_flush) + rfi_flush_enable(enable); } #endif /* CONFIG_PPC_BOOK3S_64 */ -- 2.14.3