[RFC Patch 3/7] x86: Introduce MULTIKERNEL_VECTOR for inter-kernel communication

Cong Wang
2025-09-18T22:26:26Z

From: Cong Wang <cwang@multikernel.io>

This patch adds a dedicated IPI vector (0xea) for multikernel
communication, enabling different kernel instances running on
separate CPUs to send interrupts to each other.

The implementation includes:

- MULTIKERNEL_VECTOR definition at interrupt vector 0xea
- IDT entry declaration and registration for sysvec_multikernel
- Interrupt handler sysvec_multikernel() with proper APIC EOI
and IRQ statistics tracking
- Placeholder generic_multikernel_interrupt() function for
extensible multikernel interrupt handling

This vector provides the foundational interrupt mechanism required
for implementing inter-kernel communication protocols in multikernel
environments, where heterogeneous kernel instances coordinate while
maintaining CPU-level isolation.

Signed-off-by: Cong Wang <cwang@multikernel.io>
---
arch/x86/include/asm/idtentry.h | 1 +
arch/x86/include/asm/irq_vectors.h | 1 +
arch/x86/kernel/idt.c | 1 +
arch/x86/kernel/smp.c | 12 ++++++++++++
4 files changed, 15 insertions(+)

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index a4ec27c67988..219ee36def33 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -708,6 +708,7 @@ DECLARE_IDTENTRY(RESCHEDULE_VECTOR, sysvec_reschedule_ipi);
DECLARE_IDTENTRY_SYSVEC(REBOOT_VECTOR, sysvec_reboot);
DECLARE_IDTENTRY_SYSVEC(CALL_FUNCTION_SINGLE_VECTOR, sysvec_call_function_single);
DECLARE_IDTENTRY_SYSVEC(CALL_FUNCTION_VECTOR, sysvec_call_function);
+DECLARE_IDTENTRY_SYSVEC(MULTIKERNEL_VECTOR, sysvec_multikernel);
#else
# define fred_sysvec_reschedule_ipi NULL
# define fred_sysvec_reboot NULL
diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index 47051871b436..478e2e2d188a 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -102,6 +102,7 @@
* the host kernel.
*/
#define POSTED_MSI_NOTIFICATION_VECTOR 0xeb
+#define MULTIKERNEL_VECTOR 0xea

#define NR_VECTORS 256

diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index f445bec516a0..063b330d9fbf 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -135,6 +135,7 @@ static const __initconst struct idt_data apic_idts[] = {
INTG(RESCHEDULE_VECTOR, asm_sysvec_reschedule_ipi),
INTG(CALL_FUNCTION_VECTOR, asm_sysvec_call_function),
INTG(CALL_FUNCTION_SINGLE_VECTOR, asm_sysvec_call_function_single),
+ INTG(MULTIKERNEL_VECTOR, asm_sysvec_multikernel),
INTG(REBOOT_VECTOR, asm_sysvec_reboot),
#endif

diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index b014e6d229f9..028cc423a772 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -272,6 +272,18 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_call_function_single)
trace_call_function_single_exit(CALL_FUNCTION_SINGLE_VECTOR);
}

+static void generic_multikernel_interrupt(void)
+{
+ pr_info("Multikernel interrupt\n");
+}
+
+DEFINE_IDTENTRY_SYSVEC(sysvec_multikernel)
+{
+ apic_eoi();
+ inc_irq_stat(irq_call_count);
+ generic_multikernel_interrupt();
+}
+
static int __init nonmi_ipi_setup(char *str)
{
smp_no_nmi_ipi = true;
--
2.34.1