[Qemu-devel] [PATCH v3 4/4] apic: Handle RH=1 and lowpri delivery mode in apic_get_delivery_bitmask()

[James Sullivan <sullivan.james.f@gmail.com>]

Added arguments to apic_get_delivery_bitmask() for msi_redir_hint and
for delivery_mode, changing calls to the function accordingly (using 0
as a default value for msi_redir_hint for non-MSI interrupts).

Modified the implementation of apic_get_delivery_bitmask() such that if
msi_redir_hint == 1 or delivery_mode == APIC_DM_LOWPRI, only the lowest
priority APIC will have its bitmask entry set (tie-breaking is
arbitrary). Delivery of APIC_DM_LOWPRI in apic_bus_deliver() is then
identical to APIC_DM_FIXED.

Removed function apic_ffs_bit() which was only called to support interim
LOWPRI delivery.

Signed-off-by: James Sullivan <sullivan.james.f@gmail.com>
---
Changes in v3:
    * Added extra argument to apic_get_delivery_bitmask() for
    delivery_mode
    * Perform lowpri arbitration in apic_get_delivery_bitmask() for RH=1
    and for APIC_DM_LOWPRI, saving the cost of the LAPIC iteration in v2
    * Deliver APIC_DM_LOWPRI identically to APIC_DM_FIXED (since the
    bitmask now accounts for arbitration implicitly)
    * Removed apic_ffs_bit() (no longer called)

 hw/intc/apic.c | 64 ++++++++++++++++++++++++----------------------------------
 1 file changed, 26 insertions(+), 38 deletions(-)

diff --git a/hw/intc/apic.c b/hw/intc/apic.c
index 9dd27b2..1fe3877 100644
--- a/hw/intc/apic.c
+++ b/hw/intc/apic.c
@@ -37,7 +37,9 @@ static APICCommonState *local_apics[MAX_APICS + 1];
 static void apic_set_irq(APICCommonState *s, int vector_num, int trigger_mode);
 static void apic_update_irq(APICCommonState *s);
 static void apic_get_delivery_bitmask(uint32_t *deliver_bitmask,
-                                      uint8_t dest, uint8_t dest_mode);
+                                      uint8_t dest, uint8_t dest_mode,
+                                      uint8_t delivery_mode,
+                                      uint8_t msi_redir_hint);
 static int apic_get_arb_pri(APICCommonState *s);
 
 /* Find first bit starting from msb */
@@ -46,12 +48,6 @@ static int apic_fls_bit(uint32_t value)
     return 31 - clz32(value);
 }
 
-/* Find first bit starting from lsb */
-static int apic_ffs_bit(uint32_t value)
-{
-    return ctz32(value);
-}
-
 static inline void apic_set_bit(uint32_t *tab, int index)
 {
     int i, mask;
@@ -258,24 +254,8 @@ static void apic_bus_deliver(const uint32_t *deliver_bitmask,
 
     switch (delivery_mode) {
         case APIC_DM_LOWPRI:
-            /* XXX: search for focus processor, arbitration */
-            {
-                int i, d;
-                d = -1;
-                for(i = 0; i < MAX_APIC_WORDS; i++) {
-                    if (deliver_bitmask[i]) {
-                        d = i * 32 + apic_ffs_bit(deliver_bitmask[i]);
-                        break;
-                    }
-                }
-                if (d >= 0) {
-                    apic_iter = local_apics[d];
-                    if (apic_iter) {
-                        apic_set_irq(apic_iter, vector_num, trigger_mode);
-                    }
-                }
-            }
-            return;
+            /* XXX: search for focus processor */
+            break;
 
         case APIC_DM_FIXED:
             break;
@@ -321,7 +301,8 @@ void apic_deliver_irq(uint8_t dest, uint8_t dest_mode, uint8_t delivery_mode,
     trace_apic_deliver_irq(dest, dest_mode, delivery_mode, vector_num,
                            trigger_mode, msi_redir_hint);
 
-    apic_get_delivery_bitmask(deliver_bitmask, dest, dest_mode);
+    apic_get_delivery_bitmask(deliver_bitmask, dest, dest_mode, delivery_mode,
+            msi_redir_hint);
     apic_bus_deliver(deliver_bitmask, delivery_mode, vector_num, trigger_mode);
 }
 
@@ -498,7 +479,9 @@ static int apic_find_dest(uint8_t dest)
 }
 
 static void apic_get_delivery_bitmask(uint32_t *deliver_bitmask,
-                                      uint8_t dest, uint8_t dest_mode)
+                                      uint8_t dest, uint8_t dest_mode,
+                                      uint8_t delivery_mode,
+                                      uint8_t msi_redir_hint)
 {
     APICCommonState *apic_iter;
     int i;
@@ -514,23 +497,27 @@ static void apic_get_delivery_bitmask(uint32_t *deliver_bitmask,
         }
     } else {
         /* XXX: cluster mode */
+        int l = -1;
         memset(deliver_bitmask, 0x00, MAX_APIC_WORDS * sizeof(uint32_t));
         for(i = 0; i < MAX_APICS; i++) {
             apic_iter = local_apics[i];
-            if (apic_iter) {
-                if (apic_iter->dest_mode == 0xf) {
-                    if (dest & apic_iter->log_dest)
-                        apic_set_bit(deliver_bitmask, i);
-                } else if (apic_iter->dest_mode == 0x0) {
-                    if ((dest & 0xf0) == (apic_iter->log_dest & 0xf0) &&
-                        (dest & apic_iter->log_dest & 0x0f)) {
-                        apic_set_bit(deliver_bitmask, i);
+            if (!apic_iter) {
+                break;
+            }
+            if (apic_match_dest(apic_iter, dest_mode, dest)) {
+                if (msi_redir_hint || delivery_mode == APIC_DM_LOWPRI) {
+                    if (l < 0 ||
+                        apic_compare_prio(apic_iter, local_apics[l]) < 0) {
+                        l = i;
                     }
+                } else {
+                    apic_set_bit(deliver_bitmask, i);
                 }
-            } else {
-                break;
             }
         }
+        if (l >= 0) {
+            apic_set_bit(deliver_bitmask, l);
+        }
     }
 }
 
@@ -563,7 +550,8 @@ static void apic_deliver(DeviceState *dev, uint8_t dest, uint8_t dest_mode,
 
     switch (dest_shorthand) {
     case 0:
-        apic_get_delivery_bitmask(deliver_bitmask, dest, dest_mode);
+        apic_get_delivery_bitmask(deliver_bitmask, dest, dest_mode,
+                delivery_mode, 0);
         break;
     case 1:
         memset(deliver_bitmask, 0x00, sizeof(deliver_bitmask));
-- 
2.3.5