Followup to: <[email protected]>
By author: Rene Herman <[email protected]>
In newsgroup: linux.dev.kernel
>
> Linus Torvalds wrote:
>
> > The real issue is the _physical_ address. Nothing else matters.
> >
> > If the TLB splitting on the fixed MTRRs is an issue, it depends entirely
> > on what physical address the kernel resides in, and the virtual address is
> > totally inconsequential.
> >
> > So playing games with virtual mapping has absolutely no upsides, and it
> > definitely has downsides.
>
> The notion was that having a fixed virtual mapping of the kernel would
> allow it to be loaded anywhere physically without needing to do actual
> address fixups. The bootloader could then for example at runtime decide
> to load the kernel at 16MB if the machine had enough memory available,
> to free up ZONE_DMA. Or not do that if running on a <= 16MB machine.
>
The only machines on which ZONE_DMA matters (machines with ISA DMA
devices) are also the ones which are likely to be <= 16 MB.
Yes, there are floppies, but I think having over 3 MB available for
floppy DMA is plenty, and floppies are FINALLY going away...
-hpa
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