Re: [PATCH] mm: Avoid overlap the fixmap area on i386

H. Peter Anvin
2014-10-28T17:24:24Z

On 10/28/2014 04:06 AM, Thomas Gleixner wrote:
>>
>> The available address we can use is lower than FIXADDR_BOOT_START. So
>> We will set the kmap boundary below the FIXADDR_BOOT_START, if configure
>> the high memory.
>>
>> If we configure the high memory, the vmalloc reserve area should end
>> up to PKMAP_BASE, otherwise should end up to FIXADDR_BOOT_START.
>
> Which is not really a problem, because the FIXADDR_BOOT area is only
> used during boot for early_ioremap() and it's unused when ioremap() is
> functional. vmalloc becomes available after early boot so the
> FIXADDR_BOOT area is available for reuse.
>

Given the very limited address space available on i386, it would be
extremely undesirable to not reuse address space when possible.

-hpa