在vfio中由ioctl (VFIO_DEVICE_GET_REGION_INFO)返回的"num_regions“是什么？

Question

我正在努力理解vfio如何在pci上工作。我读过https://www.kernel.org/doc/Documentation/vfio.txt，我正在写一个基于它的测试。在某种程度上，我的代码如下所示：

/* Get pci device information (number of regions and interrupts...) */
ret = ioctl(vfio_dev_fd, VFIO_DEVICE_GET_INFO, &device_info);
if (ret) {
        printf("  %s cannot get device info, "
                        "error %i (%s)\n", pci_addr, errno, strerror(errno));
        close(vfio_dev_fd);
        return -1;
}
printf ("found %d regions in the device\n", device_info.num_regions);

我不明白的是，最后的打印结果显示了9个区域！看看我的PCI设备的配置空间，我可以看到：

cat /sys/bus/pci/devices/0000\:06\:00.0/config | hd
00000000  e4 14 81 16 00 04 10 00  10 00 00 02 10 00 00 00  |................|
00000010  04 00 de f3 00 00 00 00  04 00 df f3 00 00 00 00  |................|
00000020  00 00 00 00 00 00 00 00  00 00 00 00 28 10 6e 02  |............(.n.|
00000030  00 00 00 00 48 00 00 00  00 00 00 00 0a 01 00 00  |....H...........|
00000040

我是PCI的新手，但我对此的解释是，这个董事会上只有两个BARSs (0和2)。我认为最大的区域数(酒吧？)在PCI上为6。

不过，有一点迹象表明我误解了什么:上面提到的内核文档指出：

对于PCI设备，配置空间是一个区域。

所以我要找的董事会有三个区域.但上面写着9..。pci_vfio的PCI区域是什么？它们是如何编号和访问的？

谢谢。

Answer 1

来自vfio.h：

/*
 * The VFIO-PCI bus driver makes use of the following fixed region and
 * IRQ index mapping.  Unimplemented regions return a size of zero.
 * Unimplemented IRQ types return a count of zero.
 */

enum {
    VFIO_PCI_BAR0_REGION_INDEX,
    VFIO_PCI_BAR1_REGION_INDEX,
    VFIO_PCI_BAR2_REGION_INDEX,
    VFIO_PCI_BAR3_REGION_INDEX,
    VFIO_PCI_BAR4_REGION_INDEX,
    VFIO_PCI_BAR5_REGION_INDEX,
    VFIO_PCI_ROM_REGION_INDEX,
    VFIO_PCI_CONFIG_REGION_INDEX,
    /*
     * Expose VGA regions defined for PCI base class 03, subclass 00.
     * This includes I/O port ranges 0x3b0 to 0x3bb and 0x3c0 to 0x3df
     * as well as the MMIO range 0xa0000 to 0xbffff.  Each implemented
     * range is found at it's identity mapped offset from the region
     * offset, for example 0x3b0 is region_info.offset + 0x3b0.  Areas
     * between described ranges are unimplemented.
     */
    VFIO_PCI_VGA_REGION_INDEX,
    VFIO_PCI_NUM_REGIONS
};

因此，这些附加区域可以提供对配置空间、选项ROM和特定于VGA的I/O的访问(端口和遗留框架缓冲区0xa0000.0 0xbffff窗口)。