On Tue, 1 Nov 2016, Lu Baolu wrote:
> +static int __init xdbc_init(void)
> +{
...
> + base = ioremap_nocache(xdbc.xhci_start, xdbc.xhci_length);
> + if (!base) {
> + xdbc_trace("failed to remap the io address\n");
> + ret = -ENOMEM;
> + goto free_and_quit;
> + }
> +
> + early_iounmap(xdbc.xhci_base, xdbc.xhci_length);
> + xdbc_trace("early mapped IO address released\n");
> +
> + xdbc.xhci_base = base;
> + offset = xhci_find_next_ext_cap(xdbc.xhci_base, 0, XHCI_EXT_CAPS_DEBUG);
> + xdbc.xdbc_reg = (struct xdbc_regs __iomem *)(xdbc.xhci_base + offset);
This is broken. What prevents that
- a printk is in progress on another cpu?
- a printk happens between the unmap and storing the new base ?
Nothing AFAICT. So this needs to be done in a safe way. And just making it
oldbase = xdbc.xhci_base;
base = ioremap(....);
xdbc.xhci_base = base;
early_iounmap(oldbase);
does not work either because the compiler can rightfully cache
xdbc.xhci_base in the write related functions. The same issue with
xdbc.xdbc_reg.
Thanks,
tglx
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