PCI橋支持32/64首選項(xiàng)/無(wú)首選項(xiàng)：pci_bus 0000:00: root bus resource [bus 00-ff]pci_bus 0000:00: root bus resource [io  0x0000-0xffff] pci_bus 0000:00: root bus resource [mem 0x1000000000-0x10ffffffff] (bus address [0x00000000-0xffffffff])pci_bus 0000:00: root bus resource [mem 0x1100000000-0x11ffffffff pref] (bus address [0x00000000-0xffffffff])pci_bus 0000:00: root bus resource [mem 0x2000000000-0x2fffffffff] (bus address [0x00000000-0xfffffffff])pci_bus 0000:00: root bus resource [mem 0x3000000000-0x3fffffffff pref] (bus  address [0x00000000-0xfffffffff])掃描具有2條BAR的端點(diǎn)：pci 0000:01:00.0: BAR 2: assigned [mem 0x2100000000-0x211fffffff 64bit pref]pci 0000:01:00.0: BAR 0: assigned [mem 0x1000000000-0x100007ffff]橋顯示了窗口：pci 0000:00:00.0: PCI bridge to [bus 01]pci 0000:00:00.0:   bridge window [mem 0x1000000000-0x10000fffff]pci 0000:00:00.0:   bridge window [mem 0x2100000000-0x211fffffff 64bit pref]端點(diǎn)總結(jié)了BAR：endpoint: BAR 0 addr = 0x1000000000, size = 524287endpoint: BAR 1 addr = 0x2100000000, size = 536870911BAR1的高32位將被編程為什么？我預(yù)期為0x21，但找到0x1。這是因?yàn)閜cibios_bus_to_resource / pcibios_resource_to_bus。它標(biāo)識(shí)了3個(gè)窗口偏移：window->res->start = 1000000000 window->offset = 1000000000 window->res->end = 10FFFFFFFFwindow->res->start = 1100000000 window->offset = 1100000000 window->res->end = 11FFFFFFFFwindow->res->start = 2000000000 window->offset = 2000000000 window->res->end = 2FFFFFFFFF當(dāng)顯示上面的地址時(shí)，它會(huì)增加偏移量，而在端點(diǎn)中對(duì)BAR寄存器進(jìn)行編程時(shí)，則將其減去。因此0x2100000000變?yōu)?x100000000。使用64位地址和32位BAR可能會(huì)有意義，但是為什么使用64位BAR會(huì)正確呢？