i386/tcg: implement x2APIC registers MSR access

This commit creates apic_register_read/write which are used by both
apic_mem_read/write for MMIO access and apic_msr_read/write for MSR access.

The apic_msr_read/write returns -1 on error, accelerator can use this to
raise the appropriate exception.

Signed-off-by: Bui Quang Minh <minhquangbui99@gmail.com>
Message-Id: <20240111154404.5333-2-minhquangbui99@gmail.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/intc/apic.c

@@ -288,6 +288,13 @@ void apic_deliver_irq(uint8_t dest, uint8_t dest_mode, uint8_t delivery_mode,
     apic_bus_deliver(deliver_bitmask, delivery_mode, vector_num, trigger_mode);
 }
 
+bool is_x2apic_mode(DeviceState *dev)
+{
+    APICCommonState *s = APIC(dev);
+
+    return s->apicbase & MSR_IA32_APICBASE_EXTD;
+}
+
 static void apic_set_base(APICCommonState *s, uint64_t val)
 {
     s->apicbase = (val & 0xfffff000) |
@@ -636,24 +643,19 @@ static void apic_timer(void *opaque)
     apic_timer_update(s, s->next_time);
 }
 
-static uint64_t apic_mem_read(void *opaque, hwaddr addr, unsigned size)
+static int apic_register_read(int index, uint64_t *value)
 {
     DeviceState *dev;
     APICCommonState *s;
     uint32_t val;
-    int index;
-
-    if (size < 4) {
-        return 0;
-    }
+    int ret = 0;
 
     dev = cpu_get_current_apic();
     if (!dev) {
-        return 0;
+        return -1;
     }
     s = APIC(dev);
 
-    index = (addr >> 4) & 0xff;
     switch(index) {
     case 0x02: /* id */
         val = s->id << 24;
@@ -718,12 +720,46 @@ static uint64_t apic_mem_read(void *opaque, hwaddr addr, unsigned size)
     default:
         s->esr |= APIC_ESR_ILLEGAL_ADDRESS;
         val = 0;
+        ret = -1;
         break;
     }
-    trace_apic_mem_readl(addr, val);
+
+    trace_apic_register_read(index, val);
+    *value = val;
+    return ret;
+}
+
+static uint64_t apic_mem_read(void *opaque, hwaddr addr, unsigned size)
+{
+    uint64_t val;
+    int index;
+
+    if (size < 4) {
+        return 0;
+    }
+
+    index = (addr >> 4) & 0xff;
+    apic_register_read(index, &val);
+
     return val;
 }
 
+int apic_msr_read(int index, uint64_t *val)
+{
+    DeviceState *dev;
+
+    dev = cpu_get_current_apic();
+    if (!dev) {
+        return -1;
+    }
+
+    if (!is_x2apic_mode(dev)) {
+        return -1;
+    }
+
+    return apic_register_read(index, val);
+}
+
 static void apic_send_msi(MSIMessage *msi)
 {
     uint64_t addr = msi->address;
@@ -737,35 +773,18 @@ static void apic_send_msi(MSIMessage *msi)
     apic_deliver_irq(dest, dest_mode, delivery, vector, trigger_mode);
 }
 
-static void apic_mem_write(void *opaque, hwaddr addr, uint64_t val,
-                           unsigned size)
+static int apic_register_write(int index, uint64_t val)
 {
     DeviceState *dev;
     APICCommonState *s;
-    int index = (addr >> 4) & 0xff;
-
-    if (size < 4) {
-        return;
-    }
-
-    if (addr > 0xfff || !index) {
-        /* MSI and MMIO APIC are at the same memory location,
-         * but actually not on the global bus: MSI is on PCI bus
-         * APIC is connected directly to the CPU.
-         * Mapping them on the global bus happens to work because
-         * MSI registers are reserved in APIC MMIO and vice versa. */
-        MSIMessage msi = { .address = addr, .data = val };
-        apic_send_msi(&msi);
-        return;
-    }
 
     dev = cpu_get_current_apic();
     if (!dev) {
-        return;
+        return -1;
     }
     s = APIC(dev);
 
-    trace_apic_mem_writel(addr, val);
+    trace_apic_register_write(index, val);
 
     switch(index) {
     case 0x02:
@@ -839,8 +858,51 @@ static void apic_mem_write(void *opaque, hwaddr addr, uint64_t val,
         break;
     default:
         s->esr |= APIC_ESR_ILLEGAL_ADDRESS;
-        break;
+        return -1;
     }
+
+    return 0;
+}
+
+static void apic_mem_write(void *opaque, hwaddr addr, uint64_t val,
+                           unsigned size)
+{
+    int index = (addr >> 4) & 0xff;
+
+    if (size < 4) {
+        return;
+    }
+
+    if (addr > 0xfff || !index) {
+        /*
+         * MSI and MMIO APIC are at the same memory location,
+         * but actually not on the global bus: MSI is on PCI bus
+         * APIC is connected directly to the CPU.
+         * Mapping them on the global bus happens to work because
+         * MSI registers are reserved in APIC MMIO and vice versa.
+         */
+        MSIMessage msi = { .address = addr, .data = val };
+        apic_send_msi(&msi);
+        return;
+    }
+
+    apic_register_write(index, val);
+}
+
+int apic_msr_write(int index, uint64_t val)
+{
+    DeviceState *dev;
+
+    dev = cpu_get_current_apic();
+    if (!dev) {
+        return -1;
+    }
+
+    if (!is_x2apic_mode(dev)) {
+        return -1;
+    }
+
+    return apic_register_write(index, val);
 }
 
 static void apic_pre_save(APICCommonState *s)