我有一个 FPGA 卡连接到 Linux 系统上的 PCIe。我可以对 FPGA 重新编程，然后echo 1 > /sys/bus/pci/rescan我的卡就会出现在lspci.
但是 BAR 区域没有分配任何内存：
Region 0: Memory at <unassigned> (64-bit, prefetchable) [disabled] [size=32M]
Region 2: Memory at <unassigned> (64-bit, prefetchable) [disabled] [size=64M]
我pci=在 Linux 启动命令行上尝试了各种标志，但效果不大。
我怀疑 BAR 区域太大，因此 Linux 无法在地址空间中找到适当对齐的范围来映射 BAR，因为它们在启动时不存在。
这是一个正确的理论吗？是否可以告诉 Linux 为我的设备保留空间？
I am seeing this too in Linux. There is an answer on the Xilinx forums at http://forums.xilinx.com/t5/PCI-Express/Incorrect-assignment-of-64bit-BAR-addresses/td-p/347577 - your memory spaces are smallish though. Try reducing the size until you get an allocation.
Most likely your BIOS does not allow such a big memory space BAR. Actually I have never seen a real PCIe device with more than 512MB mapped into memory space. Why would you want to do this? If you think to have a reason for that, check again whether your application really requires this amount of memory being always accessible at the same time or if you could also handle this with a paging mechanism.
Your suspicion is close but it is the BIOS that is allocating the regions, not linux. As I see it the root port is given a fixed chunk of memory, if you're asking for more than is free in that chunk then you go unallocated.
只是一个疯狂的猜测：当驱动程序第一次映射它们时，这些区域被分配了地址。
Tom Keddie 说，为设备分配地址区域的是 BIOS，而不是 linux 内核。我发现有时您需要重新启动 Linux 系统才能让它映射设备。根据您配置 FPGA 的方式，您可能需要为 FPGA 提供外部电源，以便在重启时不会清除其配置。