On Fri, 3 Sep 2021 17:36:10 +0800 Kunkun Jiang <[email protected]> wrote:
> 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). What's the call path through vfio_pci_write_config() that you're relying on to get triggered to enable this and why wouldn't we just walk all sub-page BARs in vfio_pci_load_config() to resolve the issue then? It's my understanding that we do this update in write-config because it's required that the VM sizes the BAR before using it, which is not the case when we resume from migration. Thanks, Alex > 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 <[email protected]> > Reported-by: Qixin Gan <[email protected]> > Signed-off-by: Kunkun Jiang <[email protected]> > --- > 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); > }
