diff mbox series

[2/7] RISC-V: doc: Add file describing the virtual memory map

Message ID 20190327213643.23789-3-logang@deltatee.com (mailing list archive)
State New, archived
Headers show
Series RISC-V: Sparsmem, Memory Hotplug and pte_devmap for P2P | expand

Commit Message

Logan Gunthorpe March 27, 2019, 9:36 p.m. UTC 
This file is similar to the x86_64 equivalent (in
Documentation/x86/x86_64/mm.txt) and describes the virtuas address space
usage for RISC-V.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
---
 Documentation/riscv/mm.txt | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 Documentation/riscv/mm.txt

Comments

Mike Rapoport March 28, 2019, 11:49 a.m. UTC | #1 
Hi,

On Wed, Mar 27, 2019 at 03:36:38PM -0600, Logan Gunthorpe wrote:
> This file is similar to the x86_64 equivalent (in
> Documentation/x86/x86_64/mm.txt) and describes the virtuas address space
> usage for RISC-V.
> 
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Palmer Dabbelt <palmer@sifive.com>
> Cc: Albert Ou <aou@eecs.berkeley.edu>
> ---
>  Documentation/riscv/mm.txt | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
>  create mode 100644 Documentation/riscv/mm.txt
> 
> diff --git a/Documentation/riscv/mm.txt b/Documentation/riscv/mm.txt
> new file mode 100644
> index 000000000000..725dc85f2c65
> --- /dev/null
> +++ b/Documentation/riscv/mm.txt
> @@ -0,0 +1,24 @@
> +Sv32:
> +
> +00000000 - 7fffffff   user space, different per mm (2G)
> +80000000 - 81ffffff   virtual memory map (32MB)
> +82000000 - bfffffff   vmalloc/ioremap space (1GB - 32MB)
> +c0000000 - ffffffff   direct mapping of lower phys. memory (1GB)
> +
> +Sv39:
> +
> +0000000000000000 - 0000003fffffffff  user space, different per mm (256GB)
> +hole caused by [38:63] sign extension
> +ffffffc000000000 - ffffffc0ffffffff  virtual memory map (4GB)
> +ffffffc100000000 - ffffffd0ffffffff  vmalloc/ioremap spac (64GB)
> +ffffffd100000000 - ffffffffffffffff  linear mapping of physical space (188GB)
> +  ffffffd200000000 - 0xfffffff200000000 linear mapping of all physical memory
> +
> +The RISC-V architecture defines virtual address bits in multiples of nine
> +starting from 39. These are referred to as Sv39, Sv48, Sv57 and Sv64.
> +Currently only Sv39 is supported. Bits 63 through to the most-significant
> +implemented bit are sign extended. This causes a hole between user space
> +and kernel addresses if you interpret them as unsigned.
> +
> +The direct mapping covers as much of the physical memory space as
> +possible so that it may cover some IO memory.

Please move the text before the tables, so that meaning of Sv32 and Sv39
would be clear.

> -- 
> 2.20.1
> 
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
>
Logan Gunthorpe March 28, 2019, 3:51 p.m. UTC | #2 
On 2019-03-28 5:49 a.m., Mike Rapoport wrote:
>> +
>> +The direct mapping covers as much of the physical memory space as
>> +possible so that it may cover some IO memory.
> 
> Please move the text before the tables, so that meaning of Sv32 and Sv39
> would be clear.
> 

Ok, thanks. I've queued up this change for a v2.

Logan
diff mbox series

Patch

diff --git a/Documentation/riscv/mm.txt b/Documentation/riscv/mm.txt
new file mode 100644
index 000000000000..725dc85f2c65
--- /dev/null
+++ b/Documentation/riscv/mm.txt
@@ -0,0 +1,24 @@ 
+Sv32:
+
+00000000 - 7fffffff   user space, different per mm (2G)
+80000000 - 81ffffff   virtual memory map (32MB)
+82000000 - bfffffff   vmalloc/ioremap space (1GB - 32MB)
+c0000000 - ffffffff   direct mapping of lower phys. memory (1GB)
+
+Sv39:
+
+0000000000000000 - 0000003fffffffff  user space, different per mm (256GB)
+hole caused by [38:63] sign extension
+ffffffc000000000 - ffffffc0ffffffff  virtual memory map (4GB)
+ffffffc100000000 - ffffffd0ffffffff  vmalloc/ioremap spac (64GB)
+ffffffd100000000 - ffffffffffffffff  linear mapping of physical space (188GB)
+  ffffffd200000000 - 0xfffffff200000000 linear mapping of all physical memory
+
+The RISC-V architecture defines virtual address bits in multiples of nine
+starting from 39. These are referred to as Sv39, Sv48, Sv57 and Sv64.
+Currently only Sv39 is supported. Bits 63 through to the most-significant
+implemented bit are sign extended. This causes a hole between user space
+and kernel addresses if you interpret them as unsigned.
+
+The direct mapping covers as much of the physical memory space as
+possible so that it may cover some IO memory.