hpet: Add MSI support

This implements the HPET capability of routing IRQs to the front-side
bus, aka MSI support. This feature can be enabled via the qdev property
"msi" and is off by default.

Note that switching it on can cause guests (at least Linux) to use the
HPET as timer instead of the LAPIC. KVM users should recall that only
the latter is currently available as fast in-kernel model.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

2 files changed, 37 insertions, 5 deletions

diff --git a/hw/hpet.c b/hw/hpet.c
index 6187e5e980..93fc399169 100644
--- a/hw/hpet.c
+++ b/hw/hpet.c
@@ -39,6 +39,8 @@
 #define DPRINTF(...)
 #endif
 
+#define HPET_MSI_SUPPORT        0
+
 struct HPETState;
 typedef struct HPETTimer {  /* timers */
     uint8_t tn;             /*timer number*/
@@ -47,7 +49,7 @@ typedef struct HPETTimer {  /* timers */
     /* Memory-mapped, software visible timer registers */
     uint64_t config;        /* configuration/cap */
     uint64_t cmp;           /* comparator */
-    uint64_t fsb;           /* FSB route, not supported now */
+    uint64_t fsb;           /* FSB route */
     /* Hidden register state */
     uint64_t period;        /* Last value written to comparator */
     uint8_t wrap_flag;      /* timer pop will indicate wrap for one-shot 32-bit
@@ -59,6 +61,7 @@ typedef struct HPETState {
     SysBusDevice busdev;
     uint64_t hpet_offset;
     qemu_irq irqs[HPET_NUM_IRQ_ROUTES];
+    uint32_t flags;
     uint8_t rtc_irq_level;
     uint8_t num_timers;
     HPETTimer timer[HPET_MAX_TIMERS];
@@ -80,6 +83,11 @@ static uint32_t timer_int_route(struct HPETTimer *timer)
     return (timer->config & HPET_TN_INT_ROUTE_MASK) >> HPET_TN_INT_ROUTE_SHIFT;
 }
 
+static uint32_t timer_fsb_route(HPETTimer *t)
+{
+    return t->config & HPET_TN_FSB_ENABLE;
+}
+
 static uint32_t hpet_enabled(HPETState *s)
 {
     return s->config & HPET_CFG_ENABLE;
@@ -179,7 +187,11 @@ static void update_irq(struct HPETTimer *timer, int set)
     mask = 1 << timer->tn;
     if (!set || !timer_enabled(timer) || !hpet_enabled(timer->state)) {
         s->isr &= ~mask;
-        qemu_irq_lower(s->irqs[route]);
+        if (!timer_fsb_route(timer)) {
+            qemu_irq_lower(s->irqs[route]);
+        }
+    } else if (timer_fsb_route(timer)) {
+        stl_phys(timer->fsb >> 32, timer->fsb & 0xffffffff);
     } else if (timer->config & HPET_TN_TYPE_LEVEL) {
         s->isr |= mask;
         qemu_irq_raise(s->irqs[route]);
@@ -216,6 +228,12 @@ static int hpet_post_load(void *opaque, int version_id)
     /* Push number of timers into capability returned via HPET_ID */
     s->capability &= ~HPET_ID_NUM_TIM_MASK;
     s->capability |= (s->num_timers - 1) << HPET_ID_NUM_TIM_SHIFT;
+
+    /* Derive HPET_MSI_SUPPORT from the capability of the first timer. */
+    s->flags &= ~(1 << HPET_MSI_SUPPORT);
+    if (s->timer[0].config & HPET_TN_FSB_CAP) {
+        s->flags |= 1 << HPET_MSI_SUPPORT;
+    }
     return 0;
 }
 
@@ -361,6 +379,8 @@ static uint32_t hpet_ram_readl(void *opaque, target_phys_addr_t addr)
         case HPET_TN_CMP + 4:
             return timer->cmp >> 32;
         case HPET_TN_ROUTE:
+            return timer->fsb;
+        case HPET_TN_ROUTE + 4:
             return timer->fsb >> 32;
         default:
             DPRINTF("qemu: invalid hpet_ram_readl\n");
@@ -444,6 +464,9 @@ static void hpet_ram_writel(void *opaque, target_phys_addr_t addr,
         switch ((addr - 0x100) % 0x20) {
         case HPET_TN_CFG:
             DPRINTF("qemu: hpet_ram_writel HPET_TN_CFG\n");
+            if (activating_bit(old_val, new_val, HPET_TN_FSB_ENABLE)) {
+                update_irq(timer, 0);
+            }
             val = hpet_fixup_reg(new_val, old_val, HPET_TN_CFG_WRITE_MASK);
             timer->config = (timer->config & 0xffffffff00000000ULL) | val;
             if (new_val & HPET_TN_32BIT) {
@@ -501,8 +524,11 @@ static void hpet_ram_writel(void *opaque, target_phys_addr_t addr,
                     hpet_set_timer(timer);
                 }
                 break;
+        case HPET_TN_ROUTE:
+            timer->fsb = (timer->fsb & 0xffffffff00000000ULL) | new_val;
+            break;
         case HPET_TN_ROUTE + 4:
-            DPRINTF("qemu: hpet_ram_writel HPET_TN_ROUTE + 4\n");
+            timer->fsb = (new_val << 32) | (timer->fsb & 0xffffffff);
             break;
         default:
             DPRINTF("qemu: invalid hpet_ram_writel\n");
@@ -610,7 +636,10 @@ static void hpet_reset(DeviceState *d)
 
         hpet_del_timer(timer);
         timer->cmp = ~0ULL;
-        timer->config =  HPET_TN_PERIODIC_CAP | HPET_TN_SIZE_CAP;
+        timer->config = HPET_TN_PERIODIC_CAP | HPET_TN_SIZE_CAP;
+        if (s->flags & (1 << HPET_MSI_SUPPORT)) {
+            timer->config |= HPET_TN_FSB_CAP;
+        }
         /* advertise availability of ioapic inti2 */
         timer->config |=  0x00000004ULL << 32;
         timer->period = 0ULL;
@@ -686,6 +715,7 @@ static SysBusDeviceInfo hpet_device_info = {
     .init         = hpet_init,
     .qdev.props = (Property[]) {
         DEFINE_PROP_UINT8("timers", HPETState, num_timers, HPET_MIN_TIMERS),
+        DEFINE_PROP_BIT("msi", HPETState, flags, HPET_MSI_SUPPORT, false),
         DEFINE_PROP_END_OF_LIST(),
     },
 };
diff --git a/hw/hpet_emul.h b/hw/hpet_emul.h
index e8b794c7fa..d7bc102c22 100644
--- a/hw/hpet_emul.h
+++ b/hw/hpet_emul.h
@@ -46,7 +46,9 @@
 #define HPET_TN_SETVAL           0x040
 #define HPET_TN_32BIT            0x100
 #define HPET_TN_INT_ROUTE_MASK  0x3e00
-#define HPET_TN_CFG_WRITE_MASK  0x3f4e
+#define HPET_TN_FSB_ENABLE      0x4000
+#define HPET_TN_FSB_CAP         0x8000
+#define HPET_TN_CFG_WRITE_MASK  0x7f4e
 #define HPET_TN_INT_ROUTE_SHIFT      9
 #define HPET_TN_INT_ROUTE_CAP_SHIFT 32
 #define HPET_TN_CFG_BITS_READONLY_OR_RESERVED 0xffff80b1U