现象：# echo 2 > /sys/class/infiniband/mlx5_0/device/mlx5_num_vfs

write error: Cannot allocate memory

#echo 8 > /sys/class/net/enp1s0f0/device/sriov_numvfs

write error: Cannot allocate memory

排查：

dmesg中可以看到这样错误“not enough MMIO resources for SR-IOV”

分析：

由于 BIOS 的限制或错误，PCI 代码无法重新分配足够的 MMIO。 RHEL 的 SR-IOV 支持使得它必须有足够的资源来映射所有可能的 VF，否则所有 VF MMIO 空间分配都会失败。

解决方案：

1、BIOS 没有为 VF 提供足够的 MMIO 空间。 联系您的硬件供应商获取固件或 bios 更新。

2、作为一种变通解决方案，可以在启动期间将“pci=realloc”传递给内核 2.6.32-228.el6。

实施：

在grub.cfg中添加如下红色部分：

[root@localhost ~]# cat /etc/default/grub 
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="crashkernel=auto resume=/dev/mapper/cl-swap rd.lvm.lv=cl/root rd.lvm.lv=cl/swap rhgb quiet iommu=pt intel_iommu=on pci=assign-busses pci=realloc"
GRUB_DISABLE_RECOVERY="true"
GRUB_ENABLE_BLSCFG=true
[root@localhost ~]# 

验证：

[root@localhost ~]# cat /proc/cmdline 
BOOT_IMAGE=(hd0,gpt9)/vmlinuz-4.18.0-240.22.1.el8_3.x86_64 root=/dev/mapper/cl-root ro crashkernel=auto resume=/dev/mapper/cl-swap rd.lvm.lv=cl/root rd.lvm.lv=cl/swap rhgb quiet iommu=pt intel_iommu=on pci=assign-busses pci=realloc
[root@localhost ~]# 
[root@localhost ~]# 

[root@localhost ~]# lspci
00:00.0 Host bridge: Intel Corporation Device 9b33 (rev 05)
00:01.0 PCI bridge: Intel Corporation 6th-9th Gen Core Processor PCIe Controller (x16) (rev 05)
00:02.0 VGA compatible controller: Intel Corporation Device 9bc5 (rev 05)
00:08.0 System peripheral: Intel Corporation Xeon E3-1200 v5/v6 / E3-1500 v5 / 6th/7th/8th Gen Core Processor Gaussian Mixture Model
00:12.0 Signal processing controller: Intel Corporation Comet Lake PCH Thermal Controller
00:14.0 USB controller: Intel Corporation Comet Lake USB 3.1 xHCI Host Controller
00:14.2 RAM memory: Intel Corporation Comet Lake PCH Shared SRAM
00:15.0 Serial bus controller [0c80]: Intel Corporation Comet Lake PCH Serial IO I2C Controller #0
00:16.0 Communication controller: Intel Corporation Comet Lake HECI Controller
00:17.0 SATA controller: Intel Corporation Device 06d2
00:1b.0 PCI bridge: Intel Corporation Comet Lake PCI Express Root Port #21 (rev f0)
00:1c.0 PCI bridge: Intel Corporation Device 06bd (rev f0)
00:1c.6 PCI bridge: Intel Corporation Device 06be (rev f0)
00:1f.0 ISA bridge: Intel Corporation Device 0687
00:1f.3 Audio device: Intel Corporation Comet Lake PCH cAVS
00:1f.4 SMBus: Intel Corporation Comet Lake PCH SMBus Controller
00:1f.5 Serial bus controller [0c80]: Intel Corporation Comet Lake PCH SPI Controller
00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection (11) I219-LM
01:00.0 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5]
01:00.1 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5]
01:00.2 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5 Virtual Function]
01:00.3 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5 Virtual Function]
01:00.4 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5 Virtual Function]
01:00.5 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5 Virtual Function]
02:00.0 Non-Volatile memory controller: Intel Corporation SSD 660P Series (rev 03)
03:00.0 PCI bridge: Texas Instruments XIO2001 PCI Express-to-PCI Bridge
05:00.0 Network controller: Qualcomm Atheros AR9287 Wireless Network Adapter (PCI-Express) (rev 01)
[root@localhost ~]# 

附相关命令：

#modprobe mlx5_core max_vfs=8
#mlxconfig -d /dev/mst/mt4119_pciconf0 q set SRIOV_EN=1 NUM_OF_VFS=8
#mst start    //mlx管理工具   mst status

modprobe：

options mlx4_core num_vfs=4 port_type_array=1,2 probe_vf=1

echo 0 > /sys/class/net/enp1s0f0/device/sriov_numvfs

echo 8 > /sys/class/net/enp1s0f0/device/sriov_numvfs