Commit 7b30bdca0f for qemu.org

commit 7b30bdca0f87d3089f626d81f3a39e8f8f8bd1a5
Author: Denis V. Lunev <den@openvz.org>
Date:   Thu Sep 3 20:45:41 2026 +0200

    pci: batch BAR remapping into one memory transaction

    pci_update_mappings() deletes and re-adds a subregion for each BAR
    whose address changed, and both of those commit their own transaction,
    so one BAR move costs two full flatview rebuilds.

    Nothing between the delete and the add touches an address space, so
    the walk can run inside a single transaction. pci_bridge_update_mappings()
    already does this for the bridge windows.

    CC: Michael S. Tsirkin <mst@redhat.com>
    Signed-off-by: Denis V. Lunev <den@virtuozzo.com>
    Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
    Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
    Message-ID: <20260903184542.2629976-2-den@openvz.org>

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index c15f2b9f08..14c78e3c62 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -1742,6 +1742,8 @@ static void pci_update_mappings(PCIDevice *d)
     int i;
     pcibus_t new_addr;

+    memory_region_transaction_begin();
+
     for(i = 0; i < PCI_NUM_REGIONS; i++) {
         r = &d->io_regions[i];

@@ -1778,6 +1780,8 @@ static void pci_update_mappings(PCIDevice *d)
     }

     pci_update_vga(d);
+
+    memory_region_transaction_commit();
 }

 int pci_irq_disabled(PCIDevice *d)