1 files changed, 58 insertions, 1 deletions

diff --git a/hw/xen/xen_pt_config_init.c b/hw/xen/xen_pt_config_init.c
index a75baea870..b1ad743754 100644
--- a/hw/xen/xen_pt_config_init.c
+++ b/hw/xen/xen_pt_config_init.c
@@ -1893,6 +1893,10 @@ static int xen_pt_config_reg_init(XenPCIPassthroughState *s,
     reg_entry->reg = reg;
 
     if (reg->init) {
+        uint32_t host_mask, size_mask;
+        unsigned int offset;
+        uint32_t val;
+
         /* initialize emulate register */
         rc = reg->init(s, reg_entry->reg,
                        reg_grp->base_offset + reg->offset, &data);
@@ -1905,8 +1909,61 @@ static int xen_pt_config_reg_init(XenPCIPassthroughState *s,
             g_free(reg_entry);
             return 0;
         }
+        /* Sync up the data to dev.config */
+        offset = reg_grp->base_offset + reg->offset;
+        size_mask = 0xFFFFFFFF >> ((4 - reg->size) << 3);
+
+        switch (reg->size) {
+        case 1: rc = xen_host_pci_get_byte(&s->real_device, offset, (uint8_t *)&val);
+                break;
+        case 2: rc = xen_host_pci_get_word(&s->real_device, offset, (uint16_t *)&val);
+                break;
+        case 4: rc = xen_host_pci_get_long(&s->real_device, offset, &val);
+                break;
+        default: assert(1);
+        }
+        if (rc) {
+            /* Serious issues when we cannot read the host values! */
+            g_free(reg_entry);
+            return rc;
+        }
+        /* Set bits in emu_mask are the ones we emulate. The dev.config shall
+         * contain the emulated view of the guest - therefore we flip the mask
+         * to mask out the host values (which dev.config initially has) . */
+        host_mask = size_mask & ~reg->emu_mask;
+
+        if ((data & host_mask) != (val & host_mask)) {
+            uint32_t new_val;
+
+            /* Mask out host (including past size). */
+            new_val = val & host_mask;
+            /* Merge emulated ones (excluding the non-emulated ones). */
+            new_val |= data & host_mask;
+            /* Leave intact host and emulated values past the size - even though
+             * we do not care as we write per reg->size granularity, but for the
+             * logging below lets have the proper value. */
+            new_val |= ((val | data)) & ~size_mask;
+            XEN_PT_LOG(&s->dev,"Offset 0x%04x mismatch! Emulated=0x%04x, host=0x%04x, syncing to 0x%04x.\n",
+                       offset, data, val, new_val);
+            val = new_val;
+        } else
+            val = data;
+
+        /* This could be just pci_set_long as we don't modify the bits
+         * past reg->size, but in case this routine is run in parallel
+         * we do not want to over-write other registers. */
+        switch (reg->size) {
+        case 1: pci_set_byte(s->dev.config + offset, (uint8_t)val);
+                break;
+        case 2: pci_set_word(s->dev.config + offset, (uint16_t)val);
+                break;
+        case 4: pci_set_long(s->dev.config + offset, val);
+                break;
+        default: assert(1);
+        }
         /* set register value */
-        reg_entry->data = data;
+        reg_entry->data = val;
+
     }
     /* list add register entry */
     QLIST_INSERT_HEAD(&reg_grp->reg_tbl_list, reg_entry, entries);