linux-kernel - [RFC PATCH v3 4/7] x86/apic: Introduce Remote Action Request Operations

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Message-ID: <20250605163544.3852565-5-riel@surriel.com>
Date: Thu,  5 Jun 2025 12:35:13 -0400
From: Rik van Riel <riel@...riel.com>
To: linux-kernel@...r.kernel.org
Cc: kernel-team@...a.com,
	dave.hansen@...ux.intel.com,
	luto@...nel.org,
	peterz@...radead.org,
	bp@...en8.de,
	x86@...nel.org,
	nadav.amit@...il.com,
	seanjc@...gle.com,
	tglx@...utronix.de,
	Yu-cheng Yu <yu-cheng.yu@...el.com>,
	Rik van Riel <riel@...riel.com>
Subject: [RFC PATCH v3 4/7] x86/apic: Introduce Remote Action Request Operations

From: Yu-cheng Yu <yu-cheng.yu@...el.com>

RAR TLB flushing is started by sending a command to the APIC.
This patch adds Remote Action Request commands.

Because RAR_VECTOR is hardcoded at 0xe0, POSTED_MSI_NOTIFICATION_VECTOR
has to be lowered to 0xdf, reducing the number of available vectors by
13.

[riel: refactor after 6 years of changes, lower POSTED_MSI_NOTIFICATION_VECTOR]

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
Signed-off-by: Rik van Riel <riel@...riel.com>
---
 arch/x86/include/asm/apicdef.h     | 1 +
 arch/x86/include/asm/irq_vectors.h | 7 ++++++-
 arch/x86/include/asm/smp.h         | 1 +
 arch/x86/kernel/apic/ipi.c         | 5 +++++
 arch/x86/kernel/apic/local.h       | 3 +++
 5 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/apicdef.h b/arch/x86/include/asm/apicdef.h
index 094106b6a538..b152d45af91a 100644
--- a/arch/x86/include/asm/apicdef.h
+++ b/arch/x86/include/asm/apicdef.h
@@ -92,6 +92,7 @@
 #define		APIC_DM_LOWEST		0x00100
 #define		APIC_DM_SMI		0x00200
 #define		APIC_DM_REMRD		0x00300
+#define		APIC_DM_RAR		0x00300
 #define		APIC_DM_NMI		0x00400
 #define		APIC_DM_INIT		0x00500
 #define		APIC_DM_STARTUP		0x00600
diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index 47051871b436..52a0cf56562a 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -97,11 +97,16 @@
 
 #define LOCAL_TIMER_VECTOR		0xec
 
+/*
+ * RAR (remote action request) TLB flush
+ */
+#define RAR_VECTOR			0xe0
+
 /*
  * Posted interrupt notification vector for all device MSIs delivered to
  * the host kernel.
  */
-#define POSTED_MSI_NOTIFICATION_VECTOR	0xeb
+#define POSTED_MSI_NOTIFICATION_VECTOR	0xdf
 
 #define NR_VECTORS			 256
 
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 0c1c68039d6f..0e5ad0dc987a 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -120,6 +120,7 @@ void __noreturn mwait_play_dead(unsigned int eax_hint);
 void native_smp_send_reschedule(int cpu);
 void native_send_call_func_ipi(const struct cpumask *mask);
 void native_send_call_func_single_ipi(int cpu);
+void native_send_rar_ipi(const struct cpumask *mask);
 
 asmlinkage __visible void smp_reboot_interrupt(void);
 __visible void smp_reschedule_interrupt(struct pt_regs *regs);
diff --git a/arch/x86/kernel/apic/ipi.c b/arch/x86/kernel/apic/ipi.c
index 98a57cb4aa86..9983c42619ef 100644
--- a/arch/x86/kernel/apic/ipi.c
+++ b/arch/x86/kernel/apic/ipi.c
@@ -106,6 +106,11 @@ void apic_send_nmi_to_offline_cpu(unsigned int cpu)
 		return;
 	apic->send_IPI(cpu, NMI_VECTOR);
 }
+
+void native_send_rar_ipi(const struct cpumask *mask)
+{
+	__apic_send_IPI_mask(mask, RAR_VECTOR);
+}
 #endif /* CONFIG_SMP */
 
 static inline int __prepare_ICR2(unsigned int mask)
diff --git a/arch/x86/kernel/apic/local.h b/arch/x86/kernel/apic/local.h
index bdcf609eb283..833669174267 100644
--- a/arch/x86/kernel/apic/local.h
+++ b/arch/x86/kernel/apic/local.h
@@ -38,6 +38,9 @@ static inline unsigned int __prepare_ICR(unsigned int shortcut, int vector,
 	case NMI_VECTOR:
 		icr |= APIC_DM_NMI;
 		break;
+	case RAR_VECTOR:
+		icr |= APIC_DM_RAR;
+		break;
 	}
 	return icr;
 }
-- 
2.49.0