* Huang, Ying <[EMAIL PROTECTED]> wrote:
> This patch fixes a bug of ioremap_nocache. ioremap_nocache() will call
> __ioremap() with flags != 0 to do the real work, which will call
> change_page_attr_addr() if phys_addr + size - 1 < (end_pfn_map <<
> PAGE_SHIFT). But some pages between 0 ~ end_pfn_map << PAGE_SHIFT are
> not mapped by identity map, this will make change_page_attr_addr
> failed.
very interesting! Is this in response to a bug you've triggered?
i believe the scenario you outlne could trigger on 64-bit boxen, if they
try to ioremap an area not covered by the direct ptes:
> @@ -41,8 +41,15 @@ ioremap_change_attr(unsigned long phys_a
> if (phys_addr + size - 1 < (end_pfn_map << PAGE_SHIFT)) {
> unsigned long npages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
> unsigned long vaddr = (unsigned long) __va(phys_addr);
> + int level;
>
> /*
> + * If there is no identity map for this address,
> + * change_page_attr_addr is unnecessary
> + */
> + if (!lookup_address(vaddr, &level))
> + return err;
> + /*
and we'd incorrectly fail the ioremap() with -EINVAL, and return a hard
error to the driver - and causing broken boxes, right?
Thomas has unified most of ioremap*.c as well, and we'll make sure this
fix survives the unification. The 64-bit code limped along before by
accident, because the (pre-cleanup) 64-bit __change_page_attr() code
incorrectly returned 0 for invalid ranges:
kpte = lookup_address(address);
if (!kpte) return 0;
which masked the bug you fixed now. 32-bit always returned -EINVAL on
invalid ranges.
Ingo
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