Increasing KVM on amd64
alc at cs.rice.edu
Sun Jun 8 05:39:52 UTC 2008
Kostik Belousov wrote:
>On Sat, Jun 07, 2008 at 06:59:35PM -0500, Alan Cox wrote:
>>You can download a patch from
>>http://www.cs.rice.edu/~alc/amd64_kvm_6GB.patch that increases amd64's
>>kernel virtual address space to 6GB. This patch also increases the
>>default for the kmem map to almost 2GB. I believe that kernel loadable
>>modules still work. However, I suspect that mini-dumps are broken.
>The amd64 modules text/data/bss virtual addresses are allocated from the
>kernel_map (link_elf_obj.c, link_elf_load_file). Now, the lower end
>of the kernel_map is top-6Gb.
>Kernel code (both kernel proper and modules) is compiled for "kernel memory
>model", according to the gcc info:
>Generate code for the kernel code model. The kernel runs in the
>negative 2 GB of the address space. This model has to be used for
>Linux kernel code.
>I suspect we have a problem there.
The change to link_elf_obj.c is supposed to ensure allocation of an
address in the upper 2GB of the kernel map for the module.
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