Re: Maximum amount of physical memory Pistachio can handle on IA32

Jan,

thank you for your response.

On Wednesday 31 May 2006 11:18, Jan Stoess wrote:
> > -----Original Message-----
> > From: [email protected] [mailto:[email protected]
> > karlsruhe.de] On Behalf Of Frank Mehnert
> >
> > what is the maximum amount of physical memory Pistachio can handle on
> > IA32 systems?
>
> If you are referring to the amount of physical memory Pistachio can
> handle for user level programs: Pistachio exports up to 4GBytes physical
> RAM (minus kernel memory) to userland, if available.

Ok.

> If you're referring to the maximum amount of physical memory Pistachio
> can reserve for kernel memory: The maximum is 240 MB. Pistachio remaps
> all kernel memory in the top virtual address space, which simplifies
> virt<->phys calculations. Since virtual addresses are a scarce resource
> on IA-32, kernel memory is limited to 240 Mbytes; the default is 16
> MBytes. Pistachio uses physical pages below 256 MBytes RAM for the
> kernel memory. If there is less than 256MB RAM in the box, Pistachio
> uses the last n MBytes of physical RAM.

Ok. I ran into problems using my own bootstrapper (not kickstart) which
submitted kernel memory with physical addresses beyond 240MB to the kernel
because my test box has 2GB of RAM installed. Looking at the kickstart I
found that kickstart would most probably fail in the same way if GRUB would
not pass the mmap info to kickstart. Look at the

  if (mbi->flags.mmap)
    { ... } 
  else
    {
       /* here */
    }

branch of install_memory()). There is no check if

  end = 0x00100000ULL + mbi->mem_upper * 1024ULL

is greater than 240MB.

Frank
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