Actually, no, because we may need to double-map in the low address space per discussion at LPC. Jan Beulich <jbeulich@xxxxxxxx> wrote: >>>> "H. Peter Anvin" <hpa@xxxxxxxxx> 10/05/12 6:28 PM >>> >>On 10/04/2012 11:39 PM, Jan Beulich wrote: >>>> >>>> We should have the check, but at least for Linux support we require >>>> P <= V-2. >>> >>> Not really imo - P <= V - 1 should be sufficient here, as all that >is >>> necessary is that the result represents a 1:1 mapping. Specifically, >>> there's no constraint to the virtual space limitation of the direct >>> mapping of RAM. >>> >> >>The P <= V-2 limitation doesn't come from this, it comes from the fact > >>that we need to have the regular kernel 1:1 map and still have space >for >>the kernel, vmalloc, ioremap and so on in the kernel part of the >address >>space; in theory it *could* be some fraction between 1 and 2, but >since >>hardware doesn't do fractional bits very well the above is what we >have >>been telling the hardware folks. :) > >I understand all that, but here we're talking about a true 1:1 mapping >(i.e. in the lower half of the virtual address space), as opposed to >the >direct mapping (in the upper half). We can obviously use all of the >lower >half for this purpose. > >Jan -- Sent from my mobile phone. Please excuse brevity and lack of formatting. -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
