[PATCH v2] x86/irq: introduce APIC_VECTOR_VALID()

[dmkhn@xxxxxxxxx]

Add new macro APIC_VECTOR_VALID() to validate the interrupt vector
range as per [1]. This macro replaces hardcoded checks against the
open-coded value 16 in LAPIC and virtual LAPIC code and simplifies
the code a bit.

[1] Intel SDM volume 3A
    Chapter "ADVANCED PROGRAMMABLE INTERRUPT CONTROLLER"
    Section "Valid Interrupt Vectors"

Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
Changes v1->v2:
- update APIC_VECTOR_VALID to a macro w/ parameter
- CI: https://gitlab.com/xen-project/people/dmukhin/xen/-/pipelines/1727330658
- Link to v1: 
https://lore.kernel.org/xen-devel/20250315010033.2917197-4-dmukhin@xxxxxxxx/
---
 xen/arch/x86/cpu/mcheck/mce_intel.c |  3 +--
 xen/arch/x86/hvm/vlapic.c           | 10 +++++-----
 xen/arch/x86/include/asm/apicdef.h  |  1 +
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/cpu/mcheck/mce_intel.c 
b/xen/arch/x86/cpu/mcheck/mce_intel.c
index 07b50f8793..1e52b1ac25 100644
--- a/xen/arch/x86/cpu/mcheck/mce_intel.c
+++ b/xen/arch/x86/cpu/mcheck/mce_intel.c
@@ -135,8 +135,7 @@ static void intel_init_thermal(struct cpuinfo_x86 *c)
      * BIOS has programmed on AP based on BSP's info we saved (since BIOS
      * is required to set the same value for all threads/cores).
      */
-    if ( (val & APIC_DM_MASK) != APIC_DM_FIXED
-         || (val & APIC_VECTOR_MASK) > 0xf )
+    if ( (val & APIC_DM_MASK) != APIC_DM_FIXED || APIC_VECTOR_VALID(val) )
         apic_write(APIC_LVTTHMR, val);
 
     if ( (msr_content & (1ULL<<3))
diff --git a/xen/arch/x86/hvm/vlapic.c b/xen/arch/x86/hvm/vlapic.c
index 065b2aab5b..993e972cd7 100644
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -123,7 +123,7 @@ static void vlapic_error(struct vlapic *vlapic, unsigned 
int err_bit)
              * will end up back here.  Break the cycle by only injecting LVTERR
              * if it will succeed, and folding in RECVILL otherwise.
              */
-            if ( (lvterr & APIC_VECTOR_MASK) >= 16 )
+            if ( APIC_VECTOR_VALID(lvterr) )
                 inj = true;
             else
                 set_bit(ilog2(APIC_ESR_RECVILL), &vlapic->hw.pending_esr);
@@ -136,7 +136,7 @@ static void vlapic_error(struct vlapic *vlapic, unsigned 
int err_bit)
 
 bool vlapic_test_irq(const struct vlapic *vlapic, uint8_t vec)
 {
-    if ( unlikely(vec < 16) )
+    if ( unlikely(!APIC_VECTOR_VALID(vec)) )
         return false;
 
     if ( hvm_funcs.test_pir &&
@@ -150,7 +150,7 @@ void vlapic_set_irq(struct vlapic *vlapic, uint8_t vec, 
uint8_t trig)
 {
     struct vcpu *target = vlapic_vcpu(vlapic);
 
-    if ( unlikely(vec < 16) )
+    if ( unlikely(!APIC_VECTOR_VALID(vec)) )
     {
         vlapic_error(vlapic, ilog2(APIC_ESR_RECVILL));
         return;
@@ -523,7 +523,7 @@ void vlapic_ipi(
         struct vlapic *target = vlapic_lowest_prio(
             vlapic_domain(vlapic), vlapic, short_hand, dest, dest_mode);
 
-        if ( unlikely((icr_low & APIC_VECTOR_MASK) < 16) )
+        if ( unlikely(!APIC_VECTOR_VALID(icr_low)) )
             vlapic_error(vlapic, ilog2(APIC_ESR_SENDILL));
         else if ( target )
             vlapic_accept_irq(vlapic_vcpu(target), icr_low);
@@ -531,7 +531,7 @@ void vlapic_ipi(
     }
 
     case APIC_DM_FIXED:
-        if ( unlikely((icr_low & APIC_VECTOR_MASK) < 16) )
+        if ( unlikely(!APIC_VECTOR_VALID(icr_low)) )
         {
             vlapic_error(vlapic, ilog2(APIC_ESR_SENDILL));
             break;
diff --git a/xen/arch/x86/include/asm/apicdef.h 
b/xen/arch/x86/include/asm/apicdef.h
index 49e29ec801..7b431190d2 100644
--- a/xen/arch/x86/include/asm/apicdef.h
+++ b/xen/arch/x86/include/asm/apicdef.h
@@ -78,6 +78,7 @@
 #define                        APIC_DM_STARTUP         0x00600
 #define                        APIC_DM_EXTINT          0x00700
 #define                        APIC_VECTOR_MASK        0x000FF
+#define                        APIC_VECTOR_VALID(x)    (((x) & 
APIC_VECTOR_MASK) >= 16)
 #define                APIC_ICR2       0x310
 #define                        GET_xAPIC_DEST_FIELD(x) (((x)>>24)&0xFF)
 #define                        SET_xAPIC_DEST_FIELD(x) ((x)<<24)
-- 
2.34.1