From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 941B8CCA47C for ; Tue, 7 Jun 2022 22:36:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1383405AbiFGWfL (ORCPT ); Tue, 7 Jun 2022 18:35:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59636 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1380321AbiFGVVT (ORCPT ); Tue, 7 Jun 2022 17:21:19 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6FB9315FE1B; Tue, 7 Jun 2022 11:59:56 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id B1D34CE247A; Tue, 7 Jun 2022 18:59:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C4071C385A2; Tue, 7 Jun 2022 18:59:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1654628388; bh=o1okmvwlLbbSfG3kdZ8LEKllXVWDEzZvHhSawU1CUr4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IH0A5cJPqR37lqkyXR0HrrCjqBxG2DDhysMWhON4YosCoaZdmvzUBx6rvFmXcuqEM S0ItoWXwYEnDWeipeu0+eBp5qNkDpXx3W3BHZPU4oMmo6N8PhpLmk/jx+NFEWkN6gg Oitdg55nYuCWBeDIcEGUtTUk9/uC3XNmu4Xv35m4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexander Larsson , Javier Martinez Canillas , Ard Biesheuvel , Sasha Levin Subject: [PATCH 5.18 311/879] efi: Allow to enable EFI runtime services by default on RT Date: Tue, 7 Jun 2022 18:57:09 +0200 Message-Id: <20220607165011.873446410@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220607165002.659942637@linuxfoundation.org> References: <20220607165002.659942637@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Javier Martinez Canillas [ Upstream commit a031651ff2144a3d81d4916856c093bc1ea0a413 ] Commit d9f283ae71af ("efi: Disable runtime services on RT") disabled EFI runtime services by default when the CONFIG_PREEMPT_RT option is enabled. The rationale for that commit is that some EFI calls could take too much time, leading to large latencies which is an issue for Real-Time kernels. But a side effect of that change was that now is not possible anymore to enable the EFI runtime services by default when CONFIG_PREEMPT_RT is set, without passing an efi=runtime command line parameter to the kernel. Instead, let's add a new EFI_DISABLE_RUNTIME boolean Kconfig option, that would be set to n by default but to y if CONFIG_PREEMPT_RT is enabled. That way, the current behaviour is preserved but gives users a mechanism to enable the EFI runtimes services in their kernels if that is required. For example, if the firmware could guarantee bounded time for EFI calls. Also, having a separate boolean config could allow users to disable the EFI runtime services by default even when CONFIG_PREEMPT_RT is not set. Reported-by: Alexander Larsson Fixes: d9f283ae71af ("efi: Disable runtime services on RT") Signed-off-by: Javier Martinez Canillas Link: https://lore.kernel.org/r/20220331151654.184433-1-javierm@redhat.com Signed-off-by: Ard Biesheuvel Signed-off-by: Sasha Levin --- drivers/firmware/efi/Kconfig | 15 +++++++++++++++ drivers/firmware/efi/efi.c | 2 +- 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig index 2c3dac5ecb36..243882f5e5f9 100644 --- a/drivers/firmware/efi/Kconfig +++ b/drivers/firmware/efi/Kconfig @@ -284,3 +284,18 @@ config EFI_CUSTOM_SSDT_OVERLAYS See Documentation/admin-guide/acpi/ssdt-overlays.rst for more information. + +config EFI_DISABLE_RUNTIME + bool "Disable EFI runtime services support by default" + default y if PREEMPT_RT + help + Allow to disable the EFI runtime services support by default. This can + already be achieved by using the efi=noruntime option, but it could be + useful to have this default without any kernel command line parameter. + + The EFI runtime services are disabled by default when PREEMPT_RT is + enabled, because measurements have shown that some EFI functions calls + might take too much time to complete, causing large latencies which is + an issue for Real-Time kernels. + + This default can be overridden by using the efi=runtime option. diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index 5502e176d51b..ff57db8f8d05 100644 --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -66,7 +66,7 @@ struct mm_struct efi_mm = { struct workqueue_struct *efi_rts_wq; -static bool disable_runtime = IS_ENABLED(CONFIG_PREEMPT_RT); +static bool disable_runtime = IS_ENABLED(CONFIG_EFI_DISABLE_RUNTIME); static int __init setup_noefi(char *arg) { disable_runtime = true; -- 2.35.1