Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> --- Documentation/x86/x86_64/mm.txt | 12 +++--------- 1 file changed, 3 insertions(+), 9 deletions(-) --- a/Documentation/x86/x86_64/mm.txt +++ b/Documentation/x86/x86_64/mm.txt @@ -1,6 +1,4 @@ -<previous description obsolete, deleted> - Virtual memory map with 4 level page tables: 0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm @@ -47,8 +45,9 @@ ffffffffffe00000 - ffffffffffffffff (=2 Architecture defines a 64-bit virtual address. Implementations can support less. Currently supported are 48- and 57-bit virtual addresses. Bits 63 -through to the most-significant implemented bit are set to either all ones -or all zero. This causes hole between user space and kernel addresses. +through to the most-significant implemented bit are sign extended. +This causes hole between user space and kernel addresses if you interpret them +as unsigned. The direct mapping covers all memory in the system up to the highest memory address (this means in some cases it can also include PCI memory @@ -58,9 +57,6 @@ vmalloc space is lazily synchronized int the processes using the page fault handler, with init_top_pgt as reference. -Current X86-64 implementations support up to 46 bits of address space (64 TB), -which is our current limit. This expands into MBZ space in the page tables. - We map EFI runtime services in the 'efi_pgd' PGD in a 64Gb large virtual memory window (this size is arbitrary, it can be raised later if needed). The mappings are not part of any other kernel PGD and are only available @@ -72,5 +68,3 @@ following fixmap section. Note that if CONFIG_RANDOMIZE_MEMORY is enabled, the direct mapping of all physical memory, vmalloc/ioremap space and virtual memory map are randomized. Their order is preserved but their base will be offset early at boot time. - --Andi Kleen, Jul 2004 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
