Similar to regular BAR, drivers can use pci_resize_resource() to resize an IOV BAR to the desired size provided that is supported by the hardware, which can be queried using pci_rebar_get_possible_sizes(). This feature is based on the fact that (default VF BAR size) * (supported VF number) covers all possible resource/address ranges (rounded up to the power of 2 size). For example, the total size of the resource behind the BAR is 256GB, the supported maximum VF number is 4, the default VF BAR size should then be set to 64GB. When the enabled vf_num changes, the VF BAR size will adjust accordingly as - For 1 VF, VF BAR size is 256GB - For 2 VFs, VF BAR size is 128GB - For 4 VFs, VF BAR size is 64GB This feature is necessary to accommodate the limited address per PCI port. Lianjie Shi (1): PCI: Support VF resizable BAR drivers/pci/pci.c | 47 ++++++++++++++++++++++++++++++++++- drivers/pci/setup-res.c | 45 +++++++++++++++++++++++++++------ include/uapi/linux/pci_regs.h | 1 + 3 files changed, 85 insertions(+), 8 deletions(-) base-commit: cf87f46fd34d6c19283d9625a7822f20d90b64a4 -- 2.34.1
