PCIe BAR空间的值是谁设置的？谁分配的，什么时间分配的？

Linux系统下PCIe总线、设备的枚举，资源的分配到底是哪里进行的？一直没搞太清楚，安装参考中的方法构建文件系统，编译内核，利用Qemu调试分析这个问题如下：

内核代码是5.15.0-107-generic, 工作环境是ubuntu 22.04 server OS。

Qemu虚拟机中的PCIe相关打印和对应函数如下

[    1.510805] PCI host bridge to bus 0000:00
[    1.511680] pci_bus 0000:00: root bus resource [bus 00-ff]
[    1.512317] pci_bus 0000:00: root bus resource [io  0x0000-0x0cf7 window]
[    1.512837] pci_bus 0000:00: root bus resource [io  0x0d00-0xffff window]
[    1.513208] pci_bus 0000:00: root bus resource [mem 0x000a0000-0x000bffff window]
[    1.513717] pci_bus 0000:00: root bus resource [mem 0x08000000-0xfebfffff window]
[    1.514096] pci_bus 0000:00: root bus resource [mem 0x100000000-0x17fffffff window]
[    1.517476] pci 0000:00:00.0: [8086:1237] type 00 class 0x060000    ###pci_setup_device函数中打印
[    1.533713] pci 0000:00:01.0: [8086:7000] type 00 class 0x060100
[    1.535804] pci 0000:00:01.1: [8086:7010] type 00 class 0x010180
[    1.544586] pci 0000:00:01.1: reg 0x20: [io  0xc040-0xc04f]         ###__pci_read_base函数中打印，这了打印了地址资源信息
[    1.560891] pci 0000:00:01.1: legacy IDE quirk: reg 0x10: [io  0x01f0-0x01f7]
[    1.578515] pci 0000:00:01.1: legacy IDE quirk: reg 0x14: [io  0x03f6]
[    1.597623] pci 0000:00:01.1: legacy IDE quirk: reg 0x18: [io  0x0170-0x0177]
[    1.607952] pci 0000:00:01.1: legacy IDE quirk: reg 0x1c: [io  0x0376]
[    1.658439] pci 0000:00:01.3: [8086:7113] type 00 class 0x068000
[    1.824434] pci 0000:00:01.3: quirk: [io  0x0600-0x063f] claimed by PIIX4 ACPI
[    1.832974] pci 0000:00:01.3: quirk: [io  0x0700-0x070f] claimed by PIIX4 SMB
[    1.833937] pci 0000:00:01.3: quirk_piix4_acpi+0x0/0x170 took 11718 usecs
[    1.893098] pci 0000:00:02.0: [1234:1111] type 00 class 0x030000
[    1.934991] pci 0000:00:02.0: reg 0x10: [mem 0xfd000000-0xfdffffff pref]   
[    1.972973] pci 0000:00:02.0: reg 0x18: [mem 0xfebb0000-0xfebb0fff]
[    2.034454] pci 0000:00:02.0: reg 0x30: [mem 0xfeba0000-0xfebaffff pref]
[    2.063609] pci 0000:00:02.0: Video device with shadowed ROM at [mem 0x000c0000-0x000dffff]
[    2.153403] pci 0000:00:03.0: [8086:100e] type 00 class 0x020000
[    2.166942] pci 0000:00:03.0: reg 0x10: [mem 0xfeb80000-0xfeb9ffff]
[    2.197049] pci 0000:00:03.0: reg 0x14: [io  0xc000-0xc03f]
[    2.226955] pci 0000:00:03.0: reg 0x30: [mem 0xfeb00000-0xfeb7ffff pref]
[    2.360857] ACPI: PCI: Interrupt link LNKA configured for IRQ 10
[    2.363395] ACPI: PCI: Interrupt link LNKB configured for IRQ 10
[    2.365571] ACPI: PCI: Interrupt link LNKC configured for IRQ 11
[    2.367503] ACPI: PCI: Interrupt link LNKD configured for IRQ 11
[    2.368623] ACPI: PCI: Interrupt link LNKS configured for IRQ 9
[    2.402194] iommu: Default domain type: Translated
[    2.402507] iommu: DMA domain TLB invalidation policy: lazy mode

调用栈如下,可见是内核扫描到设备的时候setup device的时候会read pci的config

 具体细节需要分析__pci_read_base函数，通过gdb调测发现是函数__pci_read_base中下图所示的199行获取的，所以是内核从配置空间中读取的。那是谁在何时设置的呢？

 BIOS配置的。

参考：

Linux Device Driver Part IV. PCI Device | tcbbd的博客

使用 GDB + Qemu 调试 Linux 内核 | Head First eBPF

PCI设备的初始化_pci resource start-CSDN博客

Linux系统总线之PCI扫描流程_linux pcie扫描过程-CSDN博客

Linux PCIe hotplug arch analysis | Sherlock's blog (wangzhou.github.io)