[PATCHv3 2/4] arm64: entry: distinguish pNMI earlier in el0 interrupt

[Pingfan Liu]

For ease of unifying code, it is helpful to lift nmi_{enter,exit}()
housekeeping from gic_handle_nmi() to el0_interrupt(). Because
gic_handle_nmi() is called by either el1 interrupt or el0, and the
housekeeping has already been done in arch level code when el1
interrupt.

Note about the original code, which calls enter_from_user_mode() in pNMI
context. Although it is weird to call rcu_eqs_exit() in the pseudo NMI
context, it has no problem. This is due to the essentiality of pNMI, a
higher priority interrupt but not akin to NMI, which allows a break-in
at any time.

Signed-off-by: Pingfan Liu <kernelfans at gmail.com>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: Paul E. McKenney <paulmck at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: Marc Zyngier <maz at kernel.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Joey Gouly <joey.gouly at arm.com>
Cc: Sami Tolvanen <samitolvanen at google.com>
Cc: Julien Thierry <julien.thierry at arm.com>
Cc: Yuichi Ito <ito-yuichi at fujitsu.com>
Cc: rcu at vger.kernel.org
To: linux-arm-kernel at lists.infradead.org
---
 arch/arm64/kernel/entry-common.c | 35 ++++++++++++++++++++++++--------
 1 file changed, 27 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 5a1a5dd66d04..afcde43f1b73 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -429,7 +429,7 @@ asmlinkage void noinstr el1h_64_sync_handler(struct pt_regs *regs)
 	}
 }
 
-static __always_inline void __el1_pnmi(struct pt_regs *regs,
+static __always_inline void __pnmi_handler_common(struct pt_regs *regs,
 				       void (*handler)(struct pt_regs *))
 {
 	arm64_enter_nmi(regs);
@@ -437,6 +437,12 @@ static __always_inline void __el1_pnmi(struct pt_regs *regs,
 	arm64_exit_nmi(regs);
 }
 
+static __always_inline void __el1_pnmi(struct pt_regs *regs,
+				       void (*handler)(struct pt_regs *))
+{
+	__pnmi_handler_common(regs, handler);
+}
+
 static __always_inline void __el1_irq(struct pt_regs *regs,
 				      void (*handler)(struct pt_regs *))
 {
@@ -673,21 +679,34 @@ asmlinkage void noinstr el0t_64_sync_handler(struct pt_regs *regs)
 	}
 }
 
-static void noinstr el0_interrupt(struct pt_regs *regs,
-				  void (*handler)(struct pt_regs *))
+static __always_inline void __el0_pnmi(struct pt_regs *regs,
+				       void (*handler)(struct pt_regs *))
+{
+	__pnmi_handler_common(regs, handler);
+}
+
+static __always_inline void __el0_irq(struct pt_regs *regs,
+				       void (*handler)(struct pt_regs *))
 {
 	enter_from_user_mode(regs);
+	irq_enter_rcu();
+	do_interrupt_handler(regs, handler);
+	irq_exit_rcu();
+	exit_to_user_mode(regs);
+}
 
+static void noinstr el0_interrupt(struct pt_regs *regs,
+				  void (*handler)(struct pt_regs *))
+{
 	write_sysreg(DAIF_PROCCTX_NOIRQ, daif);
 
 	if (regs->pc & BIT(55))
 		arm64_apply_bp_hardening();
 
-	irq_enter_rcu();
-	do_interrupt_handler(regs, handler);
-	irq_exit_rcu();
-
-	exit_to_user_mode(regs);
+	if (IS_ENABLED(CONFIG_ARM64_PSEUDO_NMI) && is_in_pnmi(regs))
+		__el0_pnmi(regs, handler);
+	else
+		__el0_irq(regs, handler);
 }
 
 static void noinstr __el0_irq_handler_common(struct pt_regs *regs)
-- 
2.31.1