diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
index 149f68bb6e..b42acb8d7c 100644
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -233,9 +233,6 @@ static void check_pdev(const struct pci_dev *pdev)
      PCI_STATUS_REC_TARGET_ABORT | PCI_STATUS_REC_MASTER_ABORT | \
      PCI_STATUS_SIG_SYSTEM_ERROR | PCI_STATUS_DETECTED_PARITY)
     u16 val;
-    unsigned int nbars = 0, rom_pos = 0, i;
-    static const char warn[] = XENLOG_WARNING
-        "%pp disabled: %sBAR [%#lx, %#lx] overlaps with memory map\n";
 
     if ( command_mask )
     {
@@ -254,8 +251,6 @@ static void check_pdev(const struct pci_dev *pdev)
     switch ( pci_conf_read8(pdev->sbdf, PCI_HEADER_TYPE) & 0x7f )
     {
     case PCI_HEADER_TYPE_BRIDGE:
-        nbars = PCI_HEADER_BRIDGE_NR_BARS;
-        rom_pos = PCI_ROM_ADDRESS1;
         if ( !bridge_ctl_mask )
             break;
         val = pci_conf_read16(pdev->sbdf, PCI_BRIDGE_CONTROL);
@@ -272,75 +267,11 @@ static void check_pdev(const struct pci_dev *pdev)
         }
         break;
 
-    case PCI_HEADER_TYPE_NORMAL:
-        nbars = PCI_HEADER_NORMAL_NR_BARS;
-        rom_pos = PCI_ROM_ADDRESS;
-        break;
-
     case PCI_HEADER_TYPE_CARDBUS:
         /* TODO */
         break;
     }
 #undef PCI_STATUS_CHECK
-
-    /* Check if BARs overlap with other memory regions. */
-    val = pci_conf_read16(pdev->sbdf, PCI_COMMAND);
-    if ( !(val & PCI_COMMAND_MEMORY) || pdev->ignore_bars )
-        return;
-
-    pci_conf_write16(pdev->sbdf, PCI_COMMAND, val & ~PCI_COMMAND_MEMORY);
-    for ( i = 0; i < nbars; )
-    {
-        uint64_t addr, size;
-        unsigned int reg = PCI_BASE_ADDRESS_0 + i * 4;
-        int rc = 1;
-
-        if ( (pci_conf_read32(pdev->sbdf, reg) & PCI_BASE_ADDRESS_SPACE) !=
-             PCI_BASE_ADDRESS_SPACE_MEMORY )
-            goto next;
-
-        rc = pci_size_mem_bar(pdev->sbdf, reg, &addr, &size,
-                              (i == nbars - 1) ? PCI_BAR_LAST : 0);
-        if ( rc < 0 )
-            /* Unable to size, better leave memory decoding disabled. */
-            return;
-        if ( size && !pci_check_bar(pdev, maddr_to_mfn(addr),
-                                    maddr_to_mfn(addr + size - 1)) )
-        {
-            /*
-             * Return without enabling memory decoding if BAR position is not
-             * in IO suitable memory. Let the hardware domain re-position the
-             * BAR.
-             */
-            printk(warn,
-                   &pdev->sbdf, "", PFN_DOWN(addr), PFN_DOWN(addr + size - 1));
-            return;
-        }
-
- next:
-        ASSERT(rc > 0);
-        i += rc;
-    }
-
-    if ( rom_pos &&
-         (pci_conf_read32(pdev->sbdf, rom_pos) & PCI_ROM_ADDRESS_ENABLE) )
-    {
-        uint64_t addr, size;
-        int rc = pci_size_mem_bar(pdev->sbdf, rom_pos, &addr, &size,
-                                  PCI_BAR_ROM);
-
-        if ( rc < 0 )
-            return;
-        if ( size && !pci_check_bar(pdev, maddr_to_mfn(addr),
-                                    maddr_to_mfn(addr + size - 1)) )
-        {
-            printk(warn, &pdev->sbdf, "ROM ", PFN_DOWN(addr),
-                   PFN_DOWN(addr + size - 1));
-            return;
-        }
-    }
-
-    pci_conf_write16(pdev->sbdf, PCI_COMMAND, val);
 }
 
 static void apply_quirks(struct pci_dev *pdev)
diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
index eb9219a49a..d272b3f343 100644
--- a/xen/drivers/vpci/header.c
+++ b/xen/drivers/vpci/header.c
@@ -115,13 +115,18 @@ static void modify_decoding(const struct pci_dev *pdev, uint16_t cmd,
             uint32_t val = bar->addr |
                            (map ? PCI_ROM_ADDRESS_ENABLE : 0);
 
-            bar->enabled = header->rom_enabled = map;
+            if ( pci_check_bar(pdev, _mfn(PFN_DOWN(bar->addr)),
+                               _mfn(PFN_DOWN(bar->addr + bar->size - 1))) )
+                bar->enabled = map;
+            header->rom_enabled = map;
             pci_conf_write32(pdev->sbdf, rom_pos, val);
             return;
         }
 
         if ( !rom_only &&
-             (bar->type != VPCI_BAR_ROM || header->rom_enabled) )
+             (bar->type != VPCI_BAR_ROM || header->rom_enabled) &&
+             pci_check_bar(pdev, _mfn(PFN_DOWN(bar->addr)),
+                           _mfn(PFN_DOWN(bar->addr + bar->size - 1))) )
             bar->enabled = map;
     }
 
@@ -234,9 +239,19 @@ static int modify_bars(const struct pci_dev *pdev, uint16_t cmd, bool rom_only)
 
         if ( !MAPPABLE_BAR(bar) ||
              (rom_only ? bar->type != VPCI_BAR_ROM
-                       : (bar->type == VPCI_BAR_ROM && !header->rom_enabled)) )
+                       : (bar->type == VPCI_BAR_ROM && !header->rom_enabled)) ||
+             /* Skip BARs already in the requested state. */
+             bar->enabled == !!(cmd & PCI_COMMAND_MEMORY) )
             continue;
 
+        if ( !pci_check_bar(pdev, _mfn(start), _mfn(end)) )
+        {
+            printk(XENLOG_G_WARNING
+                   "%pp: not mapping BAR [%lx, %lx] invalid position\n",
+                   &pdev->sbdf, start, end);
+            continue;
+        }
+
         rc = rangeset_add_range(mem, start, end);
         if ( rc )
         {
