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From: Mohamed Mediouni <mohamed.mediouni@caramail.com>
To: linux-arm-kernel@lists.infradead.org
Cc: Mark Rutland <mark.rutland@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Hector Martin <marcan@marcan.st>,
	linux-kernel@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	Mohamed Mediouni <mohamed.mediouni@caramail.com>,
	Will Deacon <will@kernel.org>,
	Stan Skowronek <stan@corellium.com>
Subject: [RFC PATCH 2/7] arm64: kernel: Add a WFI hook.
Date: Wed, 20 Jan 2021 14:27:12 +0100
Message-ID: <20210120132717.395873-3-mohamed.mediouni@caramail.com> (raw)
In-Reply-To: <20210120132717.395873-1-mohamed.mediouni@caramail.com>

From: Stan Skowronek <stan@corellium.com>

WFI drops register state on Apple Silicon for SMP systems.

This hook will be used for a hardware workaround in the
Apple CPU start driver.

Signed-off-by: Stan Skowronek <stan@corellium.com>
Signed-off-by: Mohamed Mediouni <mohamed.mediouni@caramail.com>
---
 arch/arm64/include/asm/cpu_ops.h |  2 ++
 arch/arm64/kernel/cpu_ops.c      |  6 ++++++
 arch/arm64/kernel/process.c      | 11 +++++++++--
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/cpu_ops.h b/arch/arm64/include/asm/cpu_ops.h
index e95c4df83911..4be0fc5bcaf9 100644
--- a/arch/arm64/include/asm/cpu_ops.h
+++ b/arch/arm64/include/asm/cpu_ops.h
@@ -23,6 +23,7 @@
  * @cpu_boot:	Boots a cpu into the kernel.
  * @cpu_postboot: Optionally, perform any post-boot cleanup or necessary
  *		synchronisation. Called from the cpu being booted.
+ * @cpu_wfi:    Optionally, replace calls to WFI in default idle with this.
  * @cpu_can_disable: Determines whether a CPU can be disabled based on
  *		mechanism-specific information.
  * @cpu_disable: Prepares a cpu to die. May fail for some mechanism-specific
@@ -43,6 +44,7 @@ struct cpu_operations {
 	int		(*cpu_prepare)(unsigned int);
 	int		(*cpu_boot)(unsigned int);
 	void		(*cpu_postboot)(void);
+	void		(*cpu_wfi)(void);
 #ifdef CONFIG_HOTPLUG_CPU
 	bool		(*cpu_can_disable)(unsigned int cpu);
 	int		(*cpu_disable)(unsigned int cpu);
diff --git a/arch/arm64/kernel/cpu_ops.c b/arch/arm64/kernel/cpu_ops.c
index e133011f64b5..6979fc4490b2 100644
--- a/arch/arm64/kernel/cpu_ops.c
+++ b/arch/arm64/kernel/cpu_ops.c
@@ -19,12 +19,18 @@ extern const struct cpu_operations smp_spin_table_ops;
 extern const struct cpu_operations acpi_parking_protocol_ops;
 #endif
 extern const struct cpu_operations cpu_psci_ops;
+#ifdef CONFIG_ARCH_APPLE
+extern const struct cpu_operations cpu_apple_start_ops;
+#endif

 static const struct cpu_operations *cpu_ops[NR_CPUS] __ro_after_init;

 static const struct cpu_operations *const dt_supported_cpu_ops[] __initconst = {
 	&smp_spin_table_ops,
 	&cpu_psci_ops,
+#ifdef CONFIG_ARCH_APPLE
+	&cpu_apple_start_ops,
+#endif
 	NULL,
 };

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 34ec400288d0..611c639e20be 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -57,6 +57,7 @@
 #include <asm/processor.h>
 #include <asm/pointer_auth.h>
 #include <asm/stacktrace.h>
+#include <asm/cpu_ops.h>

 #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK)
 #include <linux/stackprotector.h>
@@ -74,8 +75,14 @@ void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);

 static void noinstr __cpu_do_idle(void)
 {
-	dsb(sy);
-	wfi();
+	const struct cpu_operations *ops = get_cpu_ops(task_cpu(current));
+
+	if (ops->cpu_wfi) {
+		ops->cpu_wfi();
+	} else {
+		dsb(sy);
+		wfi();
+	}
 }

 static void noinstr __cpu_do_idle_irqprio(void)
--
2.29.2


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  parent reply index

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-20 13:27 [RFC PATCH 0/7] Linux on Apple Silicon Mohamed Mediouni
2021-01-20 13:27 ` [RFC PATCH 1/7] arm64: kernel: FIQ support Mohamed Mediouni
2021-01-20 13:27 ` Mohamed Mediouni [this message]
2021-01-20 16:46   ` [RFC PATCH 2/7] arm64: kernel: Add a WFI hook Alexander Graf
     [not found]     ` <94C20F55-D3B8-4349-B26F-9EA8AAEBF639@caramail.com>
2021-01-21 12:33       ` Hector Martin 'marcan'
2021-01-21 10:52   ` Arnd Bergmann
2021-01-21 11:01     ` Mohamed Mediouni
2021-01-21 11:36       ` Arnd Bergmann
2021-01-20 13:27 ` [RFC PATCH 3/7] arm64: mm: use nGnRnE instead of nGnRE on Apple processors Mohamed Mediouni
2021-01-20 16:47   ` Alexander Graf
2021-01-20 18:06     ` Mohamed Mediouni
2021-01-20 18:10       ` Alexander Graf
2021-01-21 11:27   ` Will Deacon
2021-01-21 11:38     ` Arnd Bergmann
2021-01-21 11:44     ` Marc Zyngier
2021-01-21 12:47       ` Will Deacon
2021-01-21 15:12         ` Mohamed Mediouni
2021-01-21 16:25           ` Marc Zyngier
2021-01-21 17:55             ` Will Deacon
2021-01-21 18:15               ` Marc Zyngier
2021-01-21 18:22                 ` Mohamed Mediouni
2021-01-21 18:22                 ` Will Deacon
2021-01-20 13:27 ` [RFC PATCH 4/7] irqchip/apple-aic: Add support for Apple AIC Mohamed Mediouni
2021-01-20 17:11   ` Alexander Graf
2021-01-20 18:04     ` Mohamed Mediouni
2021-01-20 20:16       ` Andrew Lunn
2021-01-20 21:18   ` Stan Skowronek
2021-01-21  9:48   ` Linus Walleij
2021-01-21 10:37     ` Arnd Bergmann
2021-01-21 15:29       ` Hector Martin 'marcan'
2021-01-21 17:09         ` Rob Herring
2021-01-21 17:45       ` Rob Herring
2021-01-21 16:44     ` Rob Herring
2021-01-21 16:53   ` Hector Martin 'marcan'
2021-01-20 13:27 ` [RFC PATCH 5/7] arm64/Kconfig: Add Apple Silicon SoC platform Mohamed Mediouni
2021-01-20 13:27 ` [RFC PATCH 6/7] arm64: kernel: Apple CPU start driver Mohamed Mediouni
2021-01-21 11:14   ` Arnd Bergmann
2021-01-20 13:27 ` [RFC PATCH 7/7] irqchip/apple-aic: add SMP support to the Apple AIC driver Mohamed Mediouni
2021-01-21 12:44   ` Arnd Bergmann
2021-01-21 12:50     ` Mohamed Mediouni
2021-01-21 13:00       ` Arnd Bergmann
2021-01-21 13:01         ` Hector Martin 'marcan'
2021-01-21 13:22       ` Marc Zyngier
2021-01-21 13:32         ` Mark Rutland
2021-01-21 14:05           ` Marc Zyngier
2021-01-21 13:34         ` Mohamed Mediouni
2021-01-21 14:10           ` Marc Zyngier
2021-01-21 15:09             ` Arnd Bergmann
2021-01-21 15:18               ` Mohamed Mediouni
2021-01-21 16:40       ` Rob Herring
2021-01-21 16:43         ` Mohamed Mediouni
2021-01-21 17:37           ` Rob Herring
2021-01-21 18:08             ` Mohamed Mediouni
2021-01-21 18:57               ` Rob Herring
2021-02-02 19:15   ` Linus Walleij

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