[PATCH 4/4] x86/vPMU: don't statically reserve the interrupt vector

[Jan Beulich <jbeulich@xxxxxxxx>]

Move the setup to vPMU code, doing the allocation of a vector only when
one is actually going to be needed. With that the handler function also
doesn't need to be split across two places anymore.

Add the freed up vector to the dynamically allocatable range.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
In case down the road we also want to have a build mode with vPMU code
excluded, this may also simplify things a little there.

--- a/xen/arch/x86/apic.c
+++ b/xen/arch/x86/apic.c
@@ -1313,16 +1313,6 @@ static void cf_check error_interrupt(voi
            entries[3], entries[2], entries[1], entries[0]);
 }
 
-/*
- * This interrupt handles performance counters interrupt
- */
-
-static void cf_check pmu_interrupt(void)
-{
-    ack_APIC_irq();
-    vpmu_do_interrupt();
-}
-
 void __init apic_intr_init(void)
 {
     smp_intr_init();
@@ -1333,9 +1323,6 @@ void __init apic_intr_init(void)
     /* IPI vectors for APIC spurious and error interrupts */
     set_direct_apic_vector(SPURIOUS_APIC_VECTOR, spurious_interrupt);
     set_direct_apic_vector(ERROR_APIC_VECTOR, error_interrupt);
-
-    /* Performance Counters Interrupt */
-    set_direct_apic_vector(PMU_APIC_VECTOR, pmu_interrupt);
 }
 
 /*
--- a/xen/arch/x86/cpu/vpmu.c
+++ b/xen/arch/x86/cpu/vpmu.c
@@ -40,6 +40,8 @@ static struct arch_vpmu_ops __initdata v
 static DEFINE_SPINLOCK(vpmu_lock);
 static unsigned vpmu_count;
 
+static uint8_t __ro_after_init pmu_apic_vector;
+
 static DEFINE_PER_CPU(struct vcpu *, last_vcpu);
 
 static int __init cf_check parse_vpmu_params(const char *s)
@@ -94,7 +96,7 @@ void vpmu_lvtpc_update(uint32_t val)
 
     vpmu = vcpu_vpmu(curr);
 
-    vpmu->hw_lapic_lvtpc = PMU_APIC_VECTOR | (val & APIC_LVT_MASKED);
+    vpmu->hw_lapic_lvtpc = pmu_apic_vector | (val & APIC_LVT_MASKED);
 
     /* Postpone APIC updates for PV(H) guests if PMU interrupt is pending */
     if ( has_vlapic(curr->domain) || !vpmu->xenpmu_data ||
@@ -160,7 +162,7 @@ static inline struct vcpu *choose_hwdom_
     return hardware_domain->vcpu[idx];
 }
 
-void vpmu_do_interrupt(void)
+static void cf_check vpmu_interrupt(void)
 {
     struct vcpu *sampled = current, *sampling;
     struct vpmu_struct *vpmu;
@@ -169,6 +171,8 @@ void vpmu_do_interrupt(void)
     uint32_t vlapic_lvtpc;
 #endif
 
+    ack_APIC_irq();
+
     /*
      * dom0 will handle interrupt for special domains (e.g. idle domain) or,
      * in XENPMU_MODE_ALL, for everyone.
@@ -369,7 +373,7 @@ void vpmu_save(struct vcpu *v)
 
     vpmu_reset(vpmu, VPMU_CONTEXT_SAVE);
 
-    apic_write(APIC_LVTPC, PMU_APIC_VECTOR | APIC_LVT_MASKED);
+    apic_write(APIC_LVTPC, pmu_apic_vector | APIC_LVT_MASKED);
 }
 
 int vpmu_load(struct vcpu *v, bool from_guest)
@@ -432,7 +436,7 @@ static int vpmu_arch_initialise(struct v
         return ret;
     }
 
-    vpmu->hw_lapic_lvtpc = PMU_APIC_VECTOR | APIC_LVT_MASKED;
+    vpmu->hw_lapic_lvtpc = pmu_apic_vector | APIC_LVT_MASKED;
     vpmu_set(vpmu, VPMU_INITIALIZED);
 
     return 0;
@@ -860,6 +864,8 @@ static int __init cf_check vpmu_init(voi
         register_cpu_notifier(&cpu_nfb);
         printk(XENLOG_INFO "VPMU: version " __stringify(XENPMU_VER_MAJ) "."
                __stringify(XENPMU_VER_MIN) "\n");
+
+        alloc_direct_apic_vector(&pmu_apic_vector, vpmu_interrupt);
     }
     else
     {
--- a/xen/arch/x86/include/asm/irq-vectors.h
+++ b/xen/arch/x86/include/asm/irq-vectors.h
@@ -8,13 +8,12 @@
 #define EVENT_CHECK_VECTOR     0xfc
 #define CALL_FUNCTION_VECTOR   0xfb
 #define LOCAL_TIMER_VECTOR     0xfa
-#define PMU_APIC_VECTOR        0xf9
 /*
  * High-priority dynamically-allocated vectors. For interrupts that
  * must be higher priority than any guest-bound interrupt.
  */
 #define FIRST_HIPRIORITY_VECTOR        0xf1
-#define LAST_HIPRIORITY_VECTOR  0xf8
+#define LAST_HIPRIORITY_VECTOR  0xf9
 /* IRQ0 (timer) is statically allocated but must be high priority. */
 #define IRQ0_VECTOR             0xf0
 
--- a/xen/arch/x86/include/asm/vpmu.h
+++ b/xen/arch/x86/include/asm/vpmu.h
@@ -99,7 +99,6 @@ static inline bool vpmu_are_all_set(cons
 
 void vpmu_lvtpc_update(uint32_t val);
 int vpmu_do_msr(unsigned int msr, uint64_t *msr_content, bool is_write);
-void vpmu_do_interrupt(void);
 void vpmu_initialise(struct vcpu *v);
 void vpmu_destroy(struct vcpu *v);
 void vpmu_save(struct vcpu *v);