50 lines
1.9 KiB
Diff
50 lines
1.9 KiB
Diff
From 92130515a97aabba57c55ae1632b5f2e248a7055 Mon Sep 17 00:00:00 2001
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Message-Id: <92130515a97aabba57c55ae1632b5f2e248a7055.1596234183.git.zanussi@kernel.org>
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In-Reply-To: <378ee68279f6a7631221f2670a9298620148690d.1596234183.git.zanussi@kernel.org>
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References: <378ee68279f6a7631221f2670a9298620148690d.1596234183.git.zanussi@kernel.org>
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Thu, 26 Jul 2018 15:03:16 +0200
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Subject: [PATCH 056/329] efi: Disable runtime services on RT
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.135-rt60.tar.xz
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Based on meassurements the EFI functions get_variable /
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get_next_variable take up to 2us which looks okay.
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The functions get_time, set_time take around 10ms. Those 10ms are too
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much. Even one ms would be too much.
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Ard mentioned that SetVariable might even trigger larger latencies if
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the firware will erase flash blocks on NOR.
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The time-functions are used by efi-rtc and can be triggered during
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runtimed (either via explicit read/write or ntp sync).
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The variable write could be used by pstore.
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These functions can be disabled without much of a loss. The poweroff /
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reboot hooks may be provided by PSCI.
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Disable EFI's runtime wrappers.
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This was observed on "EFI v2.60 by SoftIron Overdrive 1000".
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Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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drivers/firmware/efi/efi.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
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index 22cf4dd07b03..a2e3e3b34562 100644
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--- a/drivers/firmware/efi/efi.c
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+++ b/drivers/firmware/efi/efi.c
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@@ -87,7 +87,7 @@ struct mm_struct efi_mm = {
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struct workqueue_struct *efi_rts_wq;
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-static bool disable_runtime;
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+static bool disable_runtime = IS_ENABLED(CONFIG_PREEMPT_RT_BASE);
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static int __init setup_noefi(char *arg)
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{
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disable_runtime = true;
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--
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2.17.1
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