[PATCH 1/2] vfio/pci: Fix vfio-pci sub-page MMIO BAR mmaping in live migration

[Kunkun Jiang]

We expand MemoryRegions of vfio-pci sub-page MMIO BARs to
vfio_pci_write_config to improve IO performance.
The MemoryRegions of destination VM will not be expanded
successful in live migration, because their addresses have
been updated in vmstate_load_state (vfio_pci_load_config).

Remove the restriction on base address change in
vfio_pci_write_config for correct mmapping sub-page MMIO
BARs. Accroding to my analysis, the remaining parameter
verification is enough.

Fixes: c5e2fb3ce4d (vfio: Add save and load functions for VFIO PCI devices)
Reported-by: Nianyao Tang <tangnianyao@huawei.com>
Reported-by: Qixin Gan <ganqixin@huawei.com>
Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
---
 hw/vfio/pci.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index e1ea1d8a23..891b211ddf 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -1189,18 +1189,12 @@ void vfio_pci_write_config(PCIDevice *pdev,
         }
     } else if (ranges_overlap(addr, len, PCI_BASE_ADDRESS_0, 24) ||
         range_covers_byte(addr, len, PCI_COMMAND)) {
-        pcibus_t old_addr[PCI_NUM_REGIONS - 1];
         int bar;
 
-        for (bar = 0; bar < PCI_ROM_SLOT; bar++) {
-            old_addr[bar] = pdev->io_regions[bar].addr;
-        }
-
         pci_default_write_config(pdev, addr, val, len);
 
         for (bar = 0; bar < PCI_ROM_SLOT; bar++) {
-            if (old_addr[bar] != pdev->io_regions[bar].addr &&
-                vdev->bars[bar].region.size > 0 &&
+            if (vdev->bars[bar].region.size > 0 &&
                 vdev->bars[bar].region.size < qemu_real_host_page_size) {
                 vfio_sub_page_bar_update_mapping(pdev, bar);
             }
-- 
2.23.0