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Date: Sat, 6 Oct 2018 23:02:40 +0800
From: Baoquan He <bhe@...hat.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
linux-doc@...r.kernel.org, tglx@...utronix.de, thgarnie@...gle.com,
corbet@....net, Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 4/3 v2] x86/mm/doc: Enhance the x86-64 virtual memory
layout descriptions
On 10/06/18 at 04:38pm, Ingo Molnar wrote:
> +Notes:
> +
> + - Negative addresses such as "-23 TB" are absolute addresses in bytes, counted down
> + from the top of the 64-bit address space. It's easier to understand the layout
> + when seen both in absolute addresses and in distance-from-top notation.
> +
> + For example 0xffffe90000000000 == -23 TB, it's 23 TB lower than the top of the
> + 64-bit address space (ffffffffffffffff).
> +
> + Note that as we get closer to the top of the address space, the notation changes
> + from TB to GB and then MB/KB.
> +
> + - "16M TB" might look weird at first sight, but it's an easier to visualize size
> + notation than "16 EB", which few will recognize at first sight as 16 exabytes.
> + It also shows it nicely how incredibly large 64-bit address space is.
Thanks, this looks much better than the old version and my change.
Reviewed-by: Baoquan He <bhe@...hat.com>
Thanks
Baoquan
> +
> +========================================================================================================================
> + Start addr | Offset | End addr | Size | VM area description
> +========================================================================================================================
> + | | | |
> + 0000000000000000 | 0 | 00007fffffffffff | 128 TB | user-space virtual memory, different per mm
> +__________________|____________|__________________|_________|___________________________________________________________
> + | | | |
> + 0000800000000000 | +128 TB | ffff7fffffffffff | ~16M TB | ... huge, almost 64 bits wide hole of non-canonical
> + | | | | virtual memory addresses up to the -128 TB
> + | | | | starting offset of kernel mappings.
> +__________________|____________|__________________|_________|___________________________________________________________
> + |
> + | Kernel-space virtual memory, shared between all processes:
> +____________________________________________________________|___________________________________________________________
> + | | | |
> + ffff800000000000 | -128 TB | ffff87ffffffffff | 8 TB | ... guard hole, also reserved for hypervisor
> + ffff880000000000 | -120 TB | ffffc7ffffffffff | 64 TB | direct mapping of all physical memory (page_offset_base)
> + ffffc80000000000 | -56 TB | ffffc8ffffffffff | 1 TB | ... unused hole
> + ffffc90000000000 | -55 TB | ffffe8ffffffffff | 32 TB | vmalloc/ioremap space (vmalloc_base)
> + ffffe90000000000 | -23 TB | ffffe9ffffffffff | 1 TB | ... unused hole
> + ffffea0000000000 | -22 TB | ffffeaffffffffff | 1 TB | virtual memory map (vmemmap_base)
> + ffffeb0000000000 | -21 TB | ffffebffffffffff | 1 TB | ... unused hole
> + ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory
> + fffffc0000000000 | -4 TB | fffffdffffffffff | 2 TB | ... unused hole
> + | | | | vaddr_end for KASLR
> + fffffe0000000000 | -2 TB | fffffe7fffffffff | 0.5 TB | cpu_entry_area mapping
> + fffffe8000000000 | -1.5 TB | fffffeffffffffff | 0.5 TB | LDT remap for PTI
> + ffffff0000000000 | -1 TB | ffffff7fffffffff | 0.5 TB | %esp fixup stacks
> +__________________|____________|__________________|_________|____________________________________________________________
> + |
> + | Identical layout to the 47-bit one from here on:
> +____________________________________________________________|____________________________________________________________
> + | | | |
> + ffffff8000000000 | -512 GB | ffffffeeffffffff | 444 GB | ... unused hole
> + ffffffef00000000 | -68 GB | fffffffeffffffff | 64 GB | EFI region mapping space
> + ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | ... unused hole
> + ffffffff80000000 | -2 GB | ffffffff9fffffff | 512 MB | kernel text mapping, mapped to physical address 0
> + ffffffff80000000 |-2048 MB | | |
> + ffffffffa0000000 |-1536 MB | fffffffffeffffff | 1520 MB | module mapping space
> + ffffffffff000000 | -16 MB | | |
> + FIXADDR_START | ~-11 MB | ffffffffff5fffff | ~0.5 MB | kernel-internal fixmap range, variable size and offset
> + ffffffffff600000 | -10 MB | ffffffffff600fff | 4 kB | legacy vsyscall ABI
> + ffffffffffe00000 | -2 MB | ffffffffffffffff | 2 MB | ... unused hole
> +__________________|____________|__________________|_________|___________________________________________________________
> +
> +
> +====================================================
> +Complete virtual memory map with 5-level page tables
> +====================================================
> +
> +Notes:
> +
> + - With 56-bit addresses, user-space memory gets expanded by a factor of 512x,
> + from 0.125 PB to 64 PB. All kernel mappings shift down to the -64 PT starting
> + offset and many of the regions expand to support the much larger physical
> + memory supported.
> +
> +========================================================================================================================
> + Start addr | Offset | End addr | Size | VM area description
> +========================================================================================================================
> + | | | |
> + 0000000000000000 | 0 | 00ffffffffffffff | 64 PB | user-space virtual memory, different per mm
> +__________________|____________|__________________|_________|___________________________________________________________
> + | | | |
> + 0000800000000000 | +64 PB | ffff7fffffffffff | ~16K PB | ... huge, still almost 64 bits wide hole of non-canonical
> + | | | | virtual memory addresses up to the -128 TB
> + | | | | starting offset of kernel mappings.
> +__________________|____________|__________________|_________|___________________________________________________________
> + |
> + | Kernel-space virtual memory, shared between all processes:
> +____________________________________________________________|___________________________________________________________
> + | | | |
> + ff00000000000000 | -64 PB | ff0fffffffffffff | 4 PB | ... guard hole, also reserved for hypervisor
> + ff10000000000000 | -60 PB | ff8fffffffffffff | 32 PB | direct mapping of all physical memory (page_offset_base)
> + ff90000000000000 | -28 PB | ff9fffffffffffff | 4 PB | LDT remap for PTI
> + ffa0000000000000 | -24 PB | ffd1ffffffffffff | 12.5 PB | vmalloc/ioremap space (vmalloc_base)
> + ffd2000000000000 | -11.5 PB | ffd3ffffffffffff | 0.5 PB | ... unused hole
> + ffd4000000000000 | -11 PB | ffd5ffffffffffff | 0.5 PB | virtual memory map (vmemmap_base)
> + ffd6000000000000 | -10.5 PB | ffdeffffffffffff | 2.25 PB | ... unused hole
> + ffdf000000000000 | -8.25 PB | fffffdffffffffff | ~8 PB | KASAN shadow memory
> + fffffc0000000000 | -4 TB | fffffdffffffffff | 2 TB | ... unused hole
> + | | | | vaddr_end for KASLR
> + fffffe0000000000 | -2 TB | fffffe7fffffffff | 0.5 TB | cpu_entry_area mapping
> + fffffe8000000000 | -1.5 TB | fffffeffffffffff | 0.5 TB | ... unused hole
> + ffffff0000000000 | -1 TB | ffffff7fffffffff | 0.5 TB | %esp fixup stacks
> +__________________|____________|__________________|_________|____________________________________________________________
> + |
> + | Identical layout to the 47-bit one from here on:
> +____________________________________________________________|____________________________________________________________
> + | | | |
> + ffffff8000000000 | -512 GB | ffffffeeffffffff | 444 GB | ... unused hole
> + ffffffef00000000 | -68 GB | fffffffeffffffff | 64 GB | EFI region mapping space
> + ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | ... unused hole
> + ffffffff80000000 | -2 GB | ffffffff9fffffff | 512 MB | kernel text mapping, mapped to physical address 0
> + ffffffff80000000 |-2048 MB | | |
> + ffffffffa0000000 |-1536 MB | fffffffffeffffff | 1520 MB | module mapping space
> + ffffffffff000000 | -16 MB | | |
> + FIXADDR_START | ~-11 MB | ffffffffff5fffff | ~0.5 MB | kernel-internal fixmap range, variable size and offset
> + ffffffffff600000 | -10 MB | ffffffffff600fff | 4 kB | legacy vsyscall ABI
> + ffffffffffe00000 | -2 MB | ffffffffffffffff | 2 MB | ... unused hole
> +__________________|____________|__________________|_________|___________________________________________________________
>
> Architecture defines a 64-bit virtual address. Implementations can support
> less. Currently supported are 48- and 57-bit virtual addresses. Bits 63
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