From:   Xin Li <xin3.li@intel.com>
To:     linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org
Cc:     tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        dave.hansen@linux.intel.com, hpa@zytor.com, peterz@infradead.org,
        andrew.cooper3@citrix.com, seanjc@google.com, pbonzini@redhat.com,
        ravi.v.shankar@intel.com
Subject: [RFC PATCH v3 05/32] x86/traps: export external_interrupt() for VMX IRQ reinjection
Date:   Thu, 23 Feb 2023 23:01:18 -0800
Message-Id: <20230224070145.3572-6-xin3.li@intel.com>
In-Reply-To: <20230224070145.3572-1-xin3.li@intel.com>
References: <20230224070145.3572-1-xin3.li@intel.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

To eliminate dispatching IRQ through the IDT, export external_interrupt()
for VMX IRQ reinjection.

Signed-off-by: Xin Li <xin3.li@intel.com>
---
 arch/x86/include/asm/traps.h |  2 ++
 arch/x86/kernel/traps.c      | 14 ++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 46f5e4e2a346..da4c21ed68b4 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 external_interrupt(struct pt_regs *regs, unsigned int vector);
+
 #endif /* _ASM_X86_TRAPS_H */
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 31ad645be2fb..cebba1f49e19 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1540,6 +1540,20 @@ 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.
+ */
+EXPORT_SYMBOL_GPL(external_interrupt);
+#endif
+
 void __init trap_init(void)
 {
 	/* Init cpu_entry_area before IST entries are set up */
-- 
2.34.1