Re: CVS commit: src/sys/arch

[Maxime Villard <max%m00nbsd.net@localhost>]

Le 20/12/2016 à 15:03, Maxime Villard a écrit :
> Module Name:	src
> Committed By:	maxv
> Date:		Tue Dec 20 14:03:15 UTC 2016
> 
> Modified Files:
> 	src/sys/arch/amd64/amd64: machdep.c
> 	src/sys/arch/i386/i386: machdep.c
> 	src/sys/arch/x86/x86: pmap.c x86_machdep.c
> 
> Log Message:
> When the i386 port was designed, the bootstrap code needed little physical
> memory, and taking it below the kernel image was fine: we had 160 free
> pages, and never allocated more than 20. With amd64 however, we create a
> direct map, and for this map we need a number of page table pages that is
> mostly proportionate to the number of physical addresses available, which
> implies that these 160 free pages may not be enough.
> 
> In particular, if the CPU does not support 1GB superpages, each 1GB chunk
> of physical memory needs a 4k page in the direct map, which means that if
> a machine has 160GB of ram, the bootstrap code allocates more than 160
> pages, thereby overwriting the I/O mem area. If we push a little further,
> if a machine has 512GB of ram, we allocate ~525 pages, and start
> overwriting the kernel text, causing the system to go crazy at boot time.
> 
> Fix this moving the physical allocation area from below the kernel to above

*by moving

> it. avail_start is now beyond the kernel, and lowmem_rsvd indicates the
> reserved low-memory pages. The area [lowmem_rsvd; IOM_BEGIN[ is
> internalized into UVM, so there is no pa loss.
> 
> The only limit now is the pa of LAPIC, which is located at ~4GB of memory,
> so it is perfectly fine.
> 
> This change theoretically adds va support for 512GB of ram; and it is a
> prerequisite if we want to support more memory anyway.
> 
> 
> To generate a diff of this commit:
> cvs rdiff -u -r1.239 -r1.240 src/sys/arch/amd64/amd64/machdep.c
> cvs rdiff -u -r1.769 -r1.770 src/sys/arch/i386/i386/machdep.c
> cvs rdiff -u -r1.233 -r1.234 src/sys/arch/x86/x86/pmap.c
> cvs rdiff -u -r1.78 -r1.79 src/sys/arch/x86/x86/x86_machdep.c
> 
> Please note that diffs are not public domain; they are subject to the
> copyright notices on the relevant files.
> 
>