[RFC PATCH 05/32] x86/traps: add exc_raise_irq() for VMX IRQ reinjection

[Xin Li]

To eliminate dispatching IRQ through the IDT, add exc_raise_irq(),
which calls external_interrupt() for IRQ reinjection.

Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
---
 arch/x86/include/asm/traps.h |  2 ++
 arch/x86/kernel/traps.c      | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 46f5e4e2a346..366b1675c033 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -56,4 +56,6 @@ void __noreturn handle_stack_overflow(struct pt_regs *regs,
 	void f (struct pt_regs *regs)
 typedef DECLARE_SYSTEM_INTERRUPT_HANDLER((*system_interrupt_handler));
 
+int exc_raise_irq(struct pt_regs *regs, u32 vector);
+
 #endif /* _ASM_X86_TRAPS_H */
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index c35dd2b4d146..99386836b02e 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1536,6 +1536,24 @@ int external_interrupt(struct pt_regs *regs, unsigned int vector)
 	return 0;
 }
 
+#if IS_ENABLED(CONFIG_KVM_INTEL)
+/*
+ * KVM VMX reinjects IRQ on its current stack, it's a sync call
+ * thus the values in the pt_regs structure are not used in
+ * executing IRQ handlers, except cs.RPL and flags.IF, which
+ * are both always 0 in the VMX IRQ reinjection context.
+ *
+ * However, the pt_regs structure is sometimes used in stack
+ * dump, e.g., show_regs(). So let the caller, i.e., KVM VMX
+ * decide how to initialize the input pt_regs structure.
+ */
+int exc_raise_irq(struct pt_regs *regs, u32 vector)
+{
+	return external_interrupt(regs, vector);
+}
+EXPORT_SYMBOL_GPL(exc_raise_irq);
+#endif
+
 void __init trap_init(void)
 {
 	/* Init cpu_entry_area before IST entries are set up */
-- 
2.34.1