还是不理解IOMMU、北桥、PCI的MMIO和ioremap

mordorwww

mordorwww 发表于 2013-11-02 08:06
只是不知道cpu虚拟地址到PCI BAR的访问映射是由谁完成的？走不走CPU的MMU？

ioremap函数是否会写页表

如果CPU读写一个没有做映射的IO地址，是否会产生内存异常，就像CPU访问一个空洞的系统内存地址一样

arbao1

//Here is my comments
phymem = pci_resource_start(pdev, 0);               //<--it retrieves the physical address preallocated(normally by u-boot) to this pci device "pdev"
    if (!request_mem_region(phymem, pci_resource_len(pdev, 0), "eth")) {   //<--is this physical address being used by others ?
        printk(KERN_ERR "eth_pci: cannot reserve PCI memory region\n");   //<-- if yes, then report error
        goto bad;
    }

    mem = (unsigned long) ioremap(phymem, pci_resource_len(pdev, 0));   //<--map the physical address to linx kernel virtual address  !
    if (!mem) {
        printk(KERN_ERR "eth_pci: cannot remap PCI memory region\n") ;
        goto bad1;
    }