【65】如何通过sys文件系统remove和probe一个PCI设备

红太狼 2023-02-23 12:17 1阅读 0赞

\\-\[0000:**00\]+-01.4**\-\[03\]--+-00.0  Intel Corporation I350 Gigabit Network Connection  
                   |                   \\-00.1  Intel Corporation I350 Gigabit Network Connection

1、手动remove一个pci设备（bus:device.function 3:0.0和3.0.1）

echo 1 > /sys/bus/pci/devices/0000\\:03\\:00.0/remove

echo 1 > /sys/bus/pci/devices/0000\\:03\\:00.1/remove

2、手动扫描pci设备

echo 1 > /sys/bus/pci/rescan

这种方法是使用的bus的rescan，会扫描所有的bus。

当然如果想更精确一点，可以使用父设备下的recan来扫描子设备，两者唯一的区别就是通过bus节点扫描会调用[pci\_find\_next\_bus][pci_find_next_bus]把系统中的所有设备都rescan一遍。

这种方法是使用的devcie的rescan，只是扫描device下级bus上的的设备

echo 1 >/sys/bus/pci/devices/0000\\**:00\\:01.4**/rescan

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70][]

3、源码到底是怎么实现呢？

[https://elixir.bootlin.com/linux/v5.3/source/drivers/pci/pci-sysfs.c][https_elixir.bootlin.com_linux_v5.3_source_drivers_pci_pci-sysfs.c]

sys文件系统的函数里面有3个节点device的remove、bus的rescan和devcie的rescan，当你往文件系统写1时就回调attribute的store函数指针：

/* interface for exporting device attributes */
    struct device_attribute {
    	struct attribute	attr;
    	ssize_t (*show)(struct device *dev, struct device_attribute *attr,
    			char *buf);
    	ssize_t (*store)(struct device *dev, struct device_attribute *attr,
    			 const char *buf, size_t count);
    };

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70 2][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70 3][]

remove主要是卸载资源和调用driver的remove

下面是通过kprobe打印出来的remove调用栈

<...>-4114  \[059\] .... 73835.573048: myprobe: (pci\_remove\_bus\_device+0x0/0x100)  
            bash-4114  \[059\] .... 73835.573066: <stack trace>  
 => pci\_remove\_bus\_device  
 => pci\_stop\_and\_remove\_bus\_device\_locked  
** => remove\_store------------------入口**  
 => kernfs\_fop\_write  
 => vfs\_write  
 => ksys\_write  
 => do\_syscall\_64  
 => entry\_SYSCALL\_64\_after\_hwframe

rescan主要干两件事

（1）分配资源

（2）调用probe

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70 4][]

kprobe打印的分配资源的调用栈  
            bash-1596  \[026\] .... 56128.977294: myprobe: (pci\_assign\_resource+0x0/0x200)  
            bash-1596  \[026\] .... 56128.977296: <stack trace>  
 => pci\_assign\_resource  
 => assign\_requested\_resources\_sorted  
 => \_\_assign\_resources\_sorted  
 => \_\_pci\_bus\_assign\_resources  
 => \_\_pci\_bus\_assign\_resources  
 => pci\_assign\_unassigned\_bus\_resources  
** => pci\_rescan\_bus  
 => rescan\_store--------------------入口**  
 => kernfs\_fop\_write  
 => vfs\_write  
 => ksys\_write  
 => do\_syscall\_64  
 => entry\_SYSCALL\_64\_after\_hwframe

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70 5][]

pci\_assign\_resource函数调用\_pci\_assign\_resource分配设备需要的resource

分配完毕打印资源情况：pci\_info(dev, "BAR %d: assigned %pR\\n", resno, res);打印出就是下面的格式

具体实现原理见

[https://blog.csdn.net/tiantao2012/article/details/68483118][https_blog.csdn.net_tiantao2012_article_details_68483118]

\[72131.692082\] pci 0000:03:00.0: BAR 0: assigned \[mem 0xef600000-0xef61ffff\]  
\[72131.692087\] pci 0000:03:00.1: BAR 0: assigned \[mem 0xef620000-0xef63ffff\]  
\[72131.692092\] pci 0000:03:00.0: BAR 3: assigned \[mem 0xef640000-0xef643fff\]  
\[72131.692097\] pci 0000:03:00.0: BAR 7: assigned \[mem 0x323a0000000-0x323a001ffff 64bit pref\]  
\[72131.692103\] pci 0000:03:00.0: BAR 10: assigned \[mem 0x323a0020000-0x323a003ffff 64bit pref\]  
\[72131.692108\] pci 0000:03:00.1: BAR 3: assigned \[mem 0xef644000-0xef647fff\]  
\[72131.692112\] pci 0000:03:00.1: BAR 7: assigned \[mem 0x323a0040000-0x323a005ffff 64bit pref\]  
\[72131.692118\] pci 0000:03:00.1: BAR 10: assigned \[mem 0x323a0060000-0x323a007ffff 64bit pref\]  
\[72131.692123\] pci 0000:03:00.0: BAR 2: assigned \[io  0x1000-0x101f\]  
\[72131.692128\] pci 0000:03:00.1: BAR 2: assigned \[io  0x1020-0x103f\]

kworker/0:2-336   \[000\] ....  4201.825660: myprobe: (pci\_enable\_resources+0x0/0x170)  
     kworker/0:2-336   \[000\] ....  4201.825671: <stack trace>  
 => pci\_enable\_resources  
 => pcibios\_enable\_device  
 => do\_pci\_enable\_device  
 => pci\_enable\_device\_flags  
 => igb\_probe  
 => **local\_pci\_probe**  
 => work\_for\_cpu\_fn  
 => process\_one\_work  
 => worker\_thread  
 => kthread  
 => ret\_from\_fork

**起worker来调用driver probe。**

bash-4872  \[026\] .... 90924.365341: myprobe: (pci\_device\_probe+0x0/0x1c0)  
            bash-4872  \[026\] .... 90924.365355: <stack trace>  
 => pci\_device\_probe  
 => really\_probe  
 => driver\_probe\_device  
 => bus\_for\_each\_drv  
 => \_\_device\_attach  
 => pci\_bus\_add\_device  
 => pci\_bus\_add\_devices  
 => pci\_bus\_add\_devices  
 **=> pci\_rescan\_bus  
 => rescan\_store--------------------入口**  
 => kernfs\_fop\_write  
 => vfs\_write  
 => ksys\_write  
 => do\_syscall\_64  
 => entry\_SYSCALL\_64\_after\_hwframe

[pci_find_next_bus]: https://elixir.bootlin.com/linux/v5.3-rc1/C/ident/pci_find_next_bus
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[https_elixir.bootlin.com_linux_v5.3_source_drivers_pci_pci-sysfs.c]: https://elixir.bootlin.com/linux/v5.3/source/drivers/pci/pci-sysfs.c
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70 4]: https://img-blog.csdnimg.cn/20200707205710533.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70 5]: https://img-blog.csdnimg.cn/20200707170949981.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg==,size_16,color_FFFFFF,t_70
[https_blog.csdn.net_tiantao2012_article_details_68483118]: https://blog.csdn.net/tiantao2012/article/details/68483118