x86/idt: Hide set_intr_gate()

set_intr_gate() is an internal function of the IDT code. The only user left
is the KVM code which replaces the pagefault handler eventually.

Provide an explicit update_intr_gate() function and make set_intr_gate()
static. While at it replace the magic number 14 in the KVM code with the
proper trap define.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170828064959.663008004@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 22 insertions, 15 deletions

diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index 33f84f29a724..1a2ba368da39 100644
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -390,7 +390,7 @@ static inline void set_desc_limit(struct desc_struct *desc, unsigned long limit)
         desc->limit1 = (limit >> 16) & 0xf;
 }
 
-void set_intr_gate(unsigned int n, const void *addr);
+void update_intr_gate(unsigned int n, const void *addr);
 void alloc_intr_gate(unsigned int n, const void *addr);
 
 extern unsigned long used_vectors[];
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index b609eac3d73c..61b490c69250 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -225,6 +225,22 @@ idt_setup_from_table(gate_desc *idt, const struct idt_data *t, int size, bool sy
         }
 }
 
+static void set_intr_gate(unsigned int n, const void *addr)
+{
+        struct idt_data data;
+
+        BUG_ON(n > 0xFF);
+
+        memset(&data, 0, sizeof(data));
+        data.vector     = n;
+        data.addr       = addr;
+        data.segment    = __KERNEL_CS;
+        data.bits.type  = GATE_INTERRUPT;
+        data.bits.p     = 1;
+
+        idt_setup_from_table(idt_table, &data, 1, false);
+}
+
 /**
  * idt_setup_early_traps - Initialize the idt table with early traps
  *
@@ -336,20 +352,11 @@ void idt_invalidate(void *addr)
         load_idt(&idt);
 }
 
-void set_intr_gate(unsigned int n, const void *addr)
+void __init update_intr_gate(unsigned int n, const void *addr)
 {
-        struct idt_data data;
-
-        BUG_ON(n > 0xFF);
-
-        memset(&data, 0, sizeof(data));
-        data.vector     = n;
-        data.addr       = addr;
-        data.segment    = __KERNEL_CS;
-        data.bits.type  = GATE_INTERRUPT;
-        data.bits.p     = 1;
-
-        idt_setup_from_table(idt_table, &data, 1, false);
+        if (WARN_ON_ONCE(!test_bit(n, used_vectors)))
+                return;
+        set_intr_gate(n, addr);
 }
 
 void alloc_intr_gate(unsigned int n, const void *addr)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 6ed9242b5fa7..874827b0d7ca 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -455,7 +455,7 @@ static int kvm_cpu_down_prepare(unsigned int cpu)
 
 static void __init kvm_apf_trap_init(void)
 {
-        set_intr_gate(14, async_page_fault);
+        update_intr_gate(X86_TRAP_PF, async_page_fault);
 }
 
 void __init kvm_guest_init(void)