[PULL,1/4] xen/MSI-X: latch MSI-X table writes

diff --git a/hw/xen/xen_pt.h b/hw/xen/xen_pt.h
index c545280..4f922f4 100644
--- a/hw/xen/xen_pt.h
+++ b/hw/xen/xen_pt.h
@@ -187,13 +187,13 @@  typedef struct XenPTMSIXEntry {
     int pirq;
     uint64_t addr;
     uint32_t data;
-    uint32_t vector_ctrl;
+    uint32_t latch[4];
     bool updated; /* indicate whether MSI ADDR or DATA is updated */
-    bool warned;  /* avoid issuing (bogus) warning more than once */
 } XenPTMSIXEntry;
 typedef struct XenPTMSIX {
     uint32_t ctrl_offset;
     bool enabled;
+    bool maskall;
     int total_entries;
     int bar_index;
     uint64_t table_base;
diff --git a/hw/xen/xen_pt_config_init.c b/hw/xen/xen_pt_config_init.c
index 3d8686d..4fd7206 100644
--- a/hw/xen/xen_pt_config_init.c
+++ b/hw/xen/xen_pt_config_init.c
@@ -1499,6 +1499,8 @@  static int xen_pt_msixctrl_reg_write(XenPCIPassthroughState *s,
         xen_pt_msix_disable(s);
     }
 
+    s->msix->maskall = *val & PCI_MSIX_FLAGS_MASKALL;
+
     debug_msix_enabled_old = s->msix->enabled;
     s->msix->enabled = !!(*val & PCI_MSIX_FLAGS_ENABLE);
     if (s->msix->enabled != debug_msix_enabled_old) {
diff --git a/hw/xen/xen_pt_msi.c b/hw/xen/xen_pt_msi.c
index 82de2bc..e10cd2a 100644
--- a/hw/xen/xen_pt_msi.c
+++ b/hw/xen/xen_pt_msi.c
@@ -25,6 +25,7 @@ 
 #define XEN_PT_GFLAGSSHIFT_DELIV_MODE     12
 #define XEN_PT_GFLAGSSHIFT_TRG_MODE       15
 
+#define latch(fld) latch[PCI_MSIX_ENTRY_##fld / sizeof(uint32_t)]
 
 /*
  * Helpers
@@ -314,7 +315,8 @@  static int msix_set_enable(XenPCIPassthroughState *s, bool enabled)
                            enabled);
 }
 
-static int xen_pt_msix_update_one(XenPCIPassthroughState *s, int entry_nr)
+static int xen_pt_msix_update_one(XenPCIPassthroughState *s, int entry_nr,
+                                  uint32_t vec_ctrl)
 {
     XenPTMSIXEntry *entry = NULL;
     int pirq;
@@ -332,6 +334,19 @@  static int xen_pt_msix_update_one(XenPCIPassthroughState *s, int entry_nr)
 
     pirq = entry->pirq;
 
+    /*
+     * Update the entry addr and data to the latest values only when the
+     * entry is masked or they are all masked, as required by the spec.
+     * Addr and data changes while the MSI-X entry is unmasked get deferred
+     * until the next masked -> unmasked transition.
+     */
+    if (pirq == XEN_PT_UNASSIGNED_PIRQ || s->msix->maskall ||
+        (vec_ctrl & PCI_MSIX_ENTRY_CTRL_MASKBIT)) {
+        entry->addr = entry->latch(LOWER_ADDR) |
+                      ((uint64_t)entry->latch(UPPER_ADDR) << 32);
+        entry->data = entry->latch(DATA);
+    }
+
     rc = msi_msix_setup(s, entry->addr, entry->data, &pirq, true, entry_nr,
                         entry->pirq == XEN_PT_UNASSIGNED_PIRQ);
     if (rc) {
@@ -357,7 +372,7 @@  int xen_pt_msix_update(XenPCIPassthroughState *s)
     int i;
 
     for (i = 0; i < msix->total_entries; i++) {
-        xen_pt_msix_update_one(s, i);
+        xen_pt_msix_update_one(s, i, msix->msix_entry[i].latch(VECTOR_CTRL));
     }
 
     return 0;
@@ -406,35 +421,15 @@  int xen_pt_msix_update_remap(XenPCIPassthroughState *s, int bar_index)
 
 static uint32_t get_entry_value(XenPTMSIXEntry *e, int offset)
 {
-    switch (offset) {
-    case PCI_MSIX_ENTRY_LOWER_ADDR:
-        return e->addr & UINT32_MAX;
-    case PCI_MSIX_ENTRY_UPPER_ADDR:
-        return e->addr >> 32;
-    case PCI_MSIX_ENTRY_DATA:
-        return e->data;
-    case PCI_MSIX_ENTRY_VECTOR_CTRL:
-        return e->vector_ctrl;
-    default:
-        return 0;
-    }
+    return !(offset % sizeof(*e->latch))
+           ? e->latch[offset / sizeof(*e->latch)] : 0;
 }
 
 static void set_entry_value(XenPTMSIXEntry *e, int offset, uint32_t val)
 {
-    switch (offset) {
-    case PCI_MSIX_ENTRY_LOWER_ADDR:
-        e->addr = (e->addr & ((uint64_t)UINT32_MAX << 32)) | val;
-        break;
-    case PCI_MSIX_ENTRY_UPPER_ADDR:
-        e->addr = (uint64_t)val << 32 | (e->addr & UINT32_MAX);
-        break;
-    case PCI_MSIX_ENTRY_DATA:
-        e->data = val;
-        break;
-    case PCI_MSIX_ENTRY_VECTOR_CTRL:
-        e->vector_ctrl = val;
-        break;
+    if (!(offset % sizeof(*e->latch)))
+    {
+        e->latch[offset / sizeof(*e->latch)] = val;
     }
 }
 
@@ -454,39 +449,26 @@  static void pci_msix_write(void *opaque, hwaddr addr,
     offset = addr % PCI_MSIX_ENTRY_SIZE;
 
     if (offset != PCI_MSIX_ENTRY_VECTOR_CTRL) {
-        const volatile uint32_t *vec_ctrl;
-
         if (get_entry_value(entry, offset) == val
             && entry->pirq != XEN_PT_UNASSIGNED_PIRQ) {
             return;
         }
 
+        entry->updated = true;
+    } else if (msix->enabled && entry->updated &&
+               !(val & PCI_MSIX_ENTRY_CTRL_MASKBIT)) {
+        const volatile uint32_t *vec_ctrl;
+
         /*
          * If Xen intercepts the mask bit access, entry->vec_ctrl may not be
          * up-to-date. Read from hardware directly.
          */
         vec_ctrl = s->msix->phys_iomem_base + entry_nr * PCI_MSIX_ENTRY_SIZE
             + PCI_MSIX_ENTRY_VECTOR_CTRL;
-
-        if (msix->enabled && !(*vec_ctrl & PCI_MSIX_ENTRY_CTRL_MASKBIT)) {
-            if (!entry->warned) {
-                entry->warned = true;
-                XEN_PT_ERR(&s->dev, "Can't update msix entry %d since MSI-X is"
-                           " already enabled.\n", entry_nr);
-            }
-            return;
-        }
-
-        entry->updated = true;
+        xen_pt_msix_update_one(s, entry_nr, *vec_ctrl);
     }
 
     set_entry_value(entry, offset, val);
-
-    if (offset == PCI_MSIX_ENTRY_VECTOR_CTRL) {
-        if (msix->enabled && !(val & PCI_MSIX_ENTRY_CTRL_MASKBIT)) {
-            xen_pt_msix_update_one(s, entry_nr);
-        }
-    }
 }
 
 static uint64_t pci_msix_read(void *opaque, hwaddr addr,